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SUSTAINABLE
OPTIONS FOR
SPORTS FIELDS
Dr. Nicholas Milne and Prof. Stephen Gray
SUSTAINABLE
OPTIONS FOR
SPORTS FIELDS
Dr. Nicholas Milne and Prof. Stephen Gray
Victoria University
i
SUSTAINABLE
OPTIONS FOR
SPORTS FIELDS
Dr. Nicholas Milne and Prof. Stephen Gray
i
Executive Summary With water shortage and climate change becoming a critical global issue the need to
reduce potable water usage and utilize non-potable water for non-potable use is
increasing. An investigation of potential options for sportsgrounds has been performed
as part of a study into sports field irrigation sponsored by the Victorian government’s
Smart Water Fund. This document represents part of this investigation and is aimed to
guide water authorities, local councils and ground managers in the making decisions with
regards to sustainability of sports facilities. In brief it looks at: different turf types with
regards to water usage, suitability and injury concerns; irrigation concerns with
scheduling and estimating water requirements; irrigation water delivery and storage;
potential health impacts of different water parameters, to humans, turf and soil;
perceptions with regards to water use; and alternative water sources.
A range of different warm- and cool-season turf were presented and a summary of their
tolerances provided. Cool-season turfs have been typically associated with sports turf in
Melbourne due to general temperature conditions, however they are more water hungry.
Typically they are more cold and frost tolerant than other turfs and more tolerant to
close mowing and shade. In general warm-season turfs have been adapted for warmer
environments and utilize less water. They are typically more heat and drought tolerant,
more salt tolerant and more wear tolerant. The main drawback is their poor cold
tolerance and tendency to enter a dormant state in winter. This leads to loss of colour
(generally towards a white or brown) and a loss of wear tolerance that is perceptually a
negative for this class of turfs. Some species, particularly hybrid couches, are able to
overcome this however and other options such as overseeding also provide potential
solutions.
The effects of different natural turfs and soils on play properties such as ball bounce
resilience and ball roll resistance were presented and generally showed little difference
between warm- and cool-season turf (it must be noted however that studies on warm-
season turfs are rare). In terms of injury rates one Australian study showed a slightly
increased injury rate on some warm-season turfs, although the increase was small.
Artificial turf is becoming more popular and in its third generation is considered
aesthetically pleasing. Its main deficiencies come in its perception by players and other
users, the heating of the surface and the chemicals that can be leached from it. Players
generally perceive the surface to be more dangerous. Studies have generally shown that
injury rates do not increase on artificial turf, although the injury type changes. Having
said this, minor injuries such as cuts and abrasions tend to be more common, but go
unreported. It is these minor injuries that effect players perceptions and ultimately
impacts on the way they play. Users have been shown to adapt to the new surface and
over time play is less affected. More important was the impact on player endurance. To
reduce major injuries, such as concussions, artificial surfaces are generally less hard and
more “springy” than natural surfaces. This leads to players tiring more quickly and
potentially impacting on the speed of a game.
The lack of evaporation from an artificial surface also gives rise to a difference in surface
temperature. Surface temperatures on artificial turfs have been reported as high as 90
ii
°C. This has to be overcome by applying water to the surface prior to use to drive
evaporative cooling of the surface.
Releases of chemical from artificial turfs have caused significant grass roots campaigns
against them in some parts of the world. In particular the concern is with volatile
organics that can be released from the turf and the supporting infill. In general no
evidence has been found that these chemicals affect players, but the community concern
remains. Of greater importance is the need to capture stormwater from the field to
prevent the leaching of these compounds and zinc to the environment.
The effective estimation of irrigation requirements is important to minimise the amount
water used. Unnecessary over-irrigation can lead to wasted water, increased losses of
nutrients and pollution of waterways. Two weather-based models for estimating
irrigation requirements were presented. Although the results from each were different
the estimation in general was proportional and either technique would be sufficient.
Techniques for measuring soil moisture content were also presented and it was also
shown that with the potential exception of heat capacity-based sensors they are all
suitable for irrigation scheduling.
Irrigation delivery is one area where significant amount of water can be wasted. The less
expensive techniques are typically more prone to wastage and human error than more
expensive technologies. In general, water savings have been sometimes seen for
subsurface drip-irrigation up to about 50%, while subirrigation has shown potential
water savings of up to 90%. Both systems do however require significant capital
expense and while maintenance requirements are generally lower, where they are
required they can be quite extensive due to the systems underground location.
While storage of irrigation water in a tank seems reasonable, many alternative water
sources are available in winter while the water is needed in summer. Other water
sources provide water regularly when it is not always needed. To optimize the efficiency
of water provided to the field, large water storages may be required. Tanks are generally
too expensive for this. Artificial lake storage and aquifer recharge are two other options
that may prove more appropriate for large storage where they can be made available.
They both can lead to some decrease in the stored water quality however and this must
be considered in case treatment is again necessary before use.
Impacts on turf and soil health from irrigation water come primarily from chemical
sources. Salinity, boron, metals, oil and grease are four of the more significant ones.
Salinity, in particular the ratio of sodium to magnesium and calcium can bring about
significant changes in soil chemistry ultimately leading it to structural collapse and
preventing water penetrating into the soil. This ultimately leads to turf death. High
salinity irrigation waters should not be applied to clay soils and are best suited to soils
classified as sandy loam or coarser.
Boron tolerance in turfs is quite high however boron from desalinated seawater may still
be significant. Where boron is a problem, removal of clipping after mowing can reduce
the impacts somewhat. Some metals, particularly copper and zinc, are present in
potentially toxic concentrations to turf in irrigation water. Avoidance of sources of these
contaminants is important or else the soil will need to be monitored to ensure a build-up
does not occur. Oil and grease can be particularly effective at decreasing the wettability
iii
of a soil and ultimately preventing irrigation. The use of surfactants can potentially
overcome this problem where it is an issue.
Human health concerns focus on bacterial considerations and treatment processes must
be chosen with this in mind. While rain water will probably not need treatment other
water sources will. It is best to work within the Australia Guidelines for Water Recycling
as this document clearly outlines strategies for reduction of potential health impacts.
Along with treatment there are protocols that are likely to be required with some water
use. The protocols are aimed at preventing staff, users and the general public from
potential pathogenic threats.
Animal and livestock health may also need to be considered where they may also utilize
the ground. Importantly, pigs cannot be allowed on a field that is irrigated with recycled
black water due to the threat from Taenia solium or pork measles. Other significant risks
include Taenia saginata in cattle, Mycobacterium paratuberculosis in cattle and sheep
and Giardia lamblia in cats and dogs. Ultimately responsible risk assessment should be
performed following the Australian Guidelines where the protection of animal is required.
Perceptions of alternative water use are generally all favourable when it comes to sports
field irrigation. Studies have placed acceptability of various waters to be use in the order
of stormwater as most acceptable followed by recycled grey water, recycled black water
and finally desalinated sea water. The reason for the low acceptability of desalinated
seawater appears to be it energy consumption and associated greenhouse gas risk.
Production of desalinated water using renewable energy sources may overcome some of
this concern.
The six water sources investigated in detail were rain (roof) water, stormwater, grey
water, black water, ground water and desalinated water.
In general only desalinated seawater is rainfall independent with grey water and black
water recycling being largely rainfall independent (although it is dependent on incoming
volumes that often decrease during water shortage) than the other three water sources.
Ground water is highly dependent on natural recharge rates often making it
unsustainable, however it can be particularly efficient when combined with aquifer
recharge of another water source for longer term water storage. The volumes of water
generated by rain water may be too low for use as an independent source, but would be
suitable when supplemented by another water source.
In terms of contamination, salinity is a major issue in recycled grey and black waters,
some ground waters and desalinated sea water. In these instances calcium addition may
be required. These saline water sources should not be used on clay soils. Salinity can be
reduced by treatments such as reverse osmosis, however these will be high in energy
costs.
Metal contaminations are generally a problem in rain and storm water treatment. They
are a function of the catchment and avoidance of copper or galvanised metals,
particularly roofing can help reduce the impact. While treatment may not be necessary,
monitoring the soil may be required where these are in high quantities.
Desalinated sea water may be potentially harmful in terms of its boron content,
depending on the desalination technique used. Where this is a concern, clippings should
be removed after mowing to ensure no build up of boron can occur.
iv
The provision of nutrients is an important aspect of grey and black water recycling. A
number of researchers have shown that recycled black water will provide all of a turf’s
phosphorus and potassium requirements and go a long way to meeting the nitrogen
requirements. Grey water will perform similarly.
Finally, any considerations of alternative water must consider all local requirements and
guidelines. This report is aimed at a Melbourne audience and therefore makes reference
to various Victorian and Australian guidelines. It is important that any planning be
considered from the point of view of the most current version of these guidelines that
can be typically found online.
v
Table of Contents CHAPTER 1 – Introduction 1
CHAPTER 2 – General Issues 4
2.1 Turf and Soil Type 4
2.1.1 Cool-Season vs Warm-Season Turf 4
2.1.2 Artificial turfs 9
2.1.3 Soil 10
2.1.4 Requirements of Surfaces for Sports 12
2.1.5 Management of Sports Turfs for Drought and Long Dry Spells 18
2.1.6 Sporting Injury, Health and Turf 20
2.2 Irrigation Water 23
2.2.1 Introduction 23
2.2.2 Irrigation Volumes 23
2.2.3 Irrigation Delivery 32
2.2.4 Storage Considerations 36
2.2.5 Turf and Soil Health 38
2.2.6 Human Health 45
2.2.7 Perceptions 57
CHAPTER 3 – Water Sources 61
3.1 Introduction 61
3.2 Rain Water/Roofwater 61
3.2.1 Introduction 61
3.2.3 Treatment 66
3.2.4 Inherent Benefits 66
3.2.5 Potential Disadvantages 67
3.2.6 Conclusions 67
3.3 Stormwater 67
3.3.1 Introduction 67
3.3.2 Quality Issues 67
3.3.3 Treatment 72
3.3.4 Inherent Advantages 74
3.3.5 Potential Disadvantages 74
3.3.6 Conclusions 75
vi
3.4 Recycled Water (Grey Water) 75
3.4.1 Introduction 75
3.4.2 Quality Issues 75
3.4.3 Treatment 78
3.4.4 Advantages 81
3.4.5 Disadvantages 81
3.4.6 Conclusions 81
3.5 Recycled Water (Black Water) 82
3.5.1 Introduction 82
3.5.2 Quality Issues 82
3.5.3 Treatment 87
3.5.4 Inherent Advantages 88
3.5.5 Potential Disadvantages 89
3.5.6 Conclusions 90
3.6 Ground Water 90
3.6.1 Introduction 90
3.6.2 Quality Issues 90
3.6.3 Treatment 92
3.6.4 Advantages 93
3.6.5 Disadvantages 93
3.6.6 Conclusions 94
3.7 Desalinated Water (Brackish Water and Sea Water) 94
3.7.1 Introduction 94
3.7.2 Treatment 94
3.7.3 Quality Issues 97
3.7.4 Inherent Advantages 98
3.7.5 Disadvantages 98
3.7.6 Conclusions 98
Chapter 4 - Conclusions 99
References 101
1
CHAPTER 1 – Introduction Water is a major global, national and local issue. While the water scarcity concerns of a
few years ago are retreating from people’s mind with increased rainfalls and the
commissioning of new desalination plants along Australia’s east coast, water will
continue to be an issue for Australia. Growing population and the potential impacts of
climate change particularly in the southeast corner of Australia. Recent restrictions in
Victoria and Queensland and ongoing ground water concerns in Western Australia should
serve as a warning to sports facilities managers of conditions that could easily occur
again in the future.
It is understandable that when water scarcity becomes an issue, saving high quality
water for drinking and domestic purposes would become a priority. The potential
substitution of non-potable water in non-potable uses cannot be ignored. However the
protection of turfgrass, particularly when used for sport is also important. Studies from
the USA have shown the turfgrass in New Mexico is actually the second highest earning
crop through membership fees of golf clubs [1]. A recent study in Australia has seen
significant community support for local sports fields and tentatively placed the social
worth of a sports field at $500,000 [2]. Coupled with the benefits of exercise and team
sports [3], there is good reason to protect sports fields and ensure continued irrigation.
While potable water is protected, a range of water sources including rain water, storm
water, grey water, recycled municipal water and brackish and sea waters would be
potentially attractive alternative. The relative long-term reliability of some of these
sources could be questionable. This is one argument for diversification of water sources
to ensure continuing reliability.
There are other potential options for water reduction however. Connellan [4] has
previously noted that water conservation in sports field irrigation should focus on the
following:
• Selection of water efficient turf species
• Management of turf to maximise water use efficiency
• Selection of a well designed irrigation system
• Management of the irrigation system to maximise efficiency
To this can easily be added:
• Management of use of the field to minimise damage and wear
This work is part of a Smart Water funded project with the aim to assist sports ground
managers in identifying suitable water reduction options and potable water
replacements. In particular the aim was to re-focus thinking of water issues from a
broader distributed environment to the local scale as shown in Figure 1.1. This highlights
the potential use of water from local facilities such as toilets and clubhouses before
looking further afield to sewer mining and decentralized (neighbourhood-sized) sewage
treatment and reuse with centralized recycled water from large city-sized sewage
treatment plants as the final option.
2
Figure 1.1 Potential water sources for sports fields based around different conceptions of the sports field’s local environment.
3
The role of this document is to highlight potential concerns and address important issues
with regards to some of the changes that can be made. These are partially of a technical
nature, but will also address health and social concerns as well as the playability of
sports on different turfs. It is hoped that the final product of this report will provide the
backbone of an information package to sports ground managers when investigating more
sustainable practices in water use.
Important Notes
The guidelines referenced throughout this document, particularly the various Australian
Guidelines for Recycled Water [5-7] were current at the time of writing, but are always
subject to review. Any decision maker should ensure that the most current guidelines
and legislation will be followed for any proposed project.
It should be noted that while water qualities are presented here for a number of water
sources, there is always variations with waters from the similar sources. While water
qualities have been assessed generally, they should serve only as a rough guide.
Format of the Report
Chapter 2 of this report focuses on the changes that can be expected from changes in
water turf and soil as well as general issues to do with irrigation water. This addresses
concerns such as general turf properties, health, playability, acceptability and irrigation
delivery and water storage. This provides the necessary background to assist the
decision-making process.
Chapter 3 assesses different water sources and their potential for use in irrigation. As
part of the project the following water sources were consider: roof water, storm water,
grey water, black water, ground water, brackish water and sea water. Specifically each
one considers major constituents, treatments and advantages and disadvantages to
using the water.
4
CHAPTER 2 – General Issues
2.1 Turf and Soil Type
One of the more common methods currently chosen to reduce water usage in sports
fields is to convert the turf species from a cool-season turf to a warm-season or artificial
turf. While this can be effective at reducing water, there may be unintended side effects
particularly with regards to playability and injury rates. The following sections are a
general discussion of the differences between turf and soil types and the changes that
can occur after transition from one type to another.
2.1.1 Cool-Season vs Warm-Season Turf
Selection of turf has typically been performed based around local climatic conditions, but
with the focus on temperature rather than rainfall. In this respect cooler climates tend to
rely on cool-season turfs that have adapted to temperatures in the range 15 to 24 °C,
while warmer climates are better suited to warm-season turfs that are adapted to
temperatures in the range 27 to 35 °C In recent times, due to the effects of drought,
water restrictions and possible impacts of climate change, this strategy is being
refocused towards water availability.
The main physical difference between warm- and cool-season turf is the direction in
which the leaf grows. Cool-season typically grow in a vertical direction while warm-
season tends to grow more horizontally [8] (note this is a generalization and there are
exceptions [9]). This ultimately means that warm season turfs give greater shading for
the soil and lower leaves and this helps to reduce the rate of evapotranspiration or water
loss from the soil (either through use/transpiration by the turf or evaporation from the
soil) [8]. Table 2.1 give the water use for seven turfgrasses over a 12 week period. It
can quickly be seen there is a significant difference between warm- and cool-season turf
species. Reduced evapotranspiration contributes to the lower irrigation requirements of
warm-season turfs and the reason why there is a drive towards replacing cool-season
turfs with warm-season varieties in Melbourne. Table 2.2 shows a list of typical warm-
and cool-season turfs and some of their properties. It is not just the amount of water
used or lost from the turf that is important to selection however, there are a range of
other parameters that are important in this respect. These include:
• Drought tolerance – This is the ability of the turf to survive long periods with less
water than is required. Typically warm-season turfs are more drought tolerant.
• Salinity tolerance – This is the ability of the turf to survive in a highly saline soil,
or with a highly saline irrigation water. Typically warm-season turfs have greater
salinity tolerance
• Wear tolerance – This is the ability of the turf to tolerate heavy traffic without
showing signs of damage. Typically warm-season turfs have a greater wear
tolerance [9].
• Recuperative potential – This is the ability for a turf to recover from damage to
use and wear. It should be noted this is the potential and not the rate, recovery
rates may vary between species that have the same recuperative potential.
• Heat tolerance – This is the ability of the turf to withstand sustained high
temperatures. Typically warm-season turfs have greater heat tolerance.
5
Table 2.1. Water use over 12 weeks for seven turfgrass species. Adapted from [10]
Turf species Water use over
12 weeks (L)
Transpiration Ratio
(g Water/g Dry Matter)
Warm-season turfs
Cynodon dactylon
Couch 33.6 308
Paspalum distichum
Seashore paspalum 36.1 343
Pennisetum clandestinium
Kikuyu 40.1 346
Buchloë dactyloides
Buffalograss 37.3 365
Zoysia japonica Japanese Lawngrass
33.7 420
Cool-season turfs
Festuca arundinacea
Tall fescue 55.9 586
Lolium perenne
Perennial ryegrass 49.6 671
• Cold tolerance – This is the ability of the turf to withstand sustained low
temperatures. Typically cool-season turfs have a greater cold tolerance.
• Frost tolerance – This is the ability of the turf to withstand frosts and ice. Cool-
season turfs are typically more frost tolerant
• Mow tolerance – This is a measure of how well a turf will survive when mowed to
a short height.
• Shade tolerance – This is the ability of a turf to survive with limited sunlight.
• Flood tolerance – This is a measure of the ability of a turf to withstand period
where it is immersed in water.
Table 2.2 gives the tolerances of important turfgrass species. It should be noted that
these are generalized descriptions and there can be significant variation within species
[8].
One of the other main differences between warm- and cool-season turfs is their periods
of dormancy. Warm-season turfs tend to be poorly tolerant of cold conditions, as noted
previously, and enter a period of dormancy, typically over winter, as a way of avoiding
these conditions. During dormancy pigment production ceases and the turf loses its
green colour [9]. This leads to a brown or white coloured turf. The extent of
discolouration varies between species with Eremochloa ophiuroides (centipedegrass)
being one of the worst performers [9]. Table 2.3 give the general trends in terms of
discolouration. Discolouration can be avoided through the application of turf colourants
(chemicals that will re-establish turf colour) [9], applications of fertilizer (although this
can be damaging to the turf, particularly over wet winters) [11] or else warm-season
turfs can be overseeded by cool-season turfs [9]. This last option may be more
appropriate due to dormancy also impacting on the wear tolerance and recuperative
potential of some turfs [9]. There are hybrid turfs that have been developed specifically
for colour retention over winter. These are typically couch hybrids (Cynodon dactylon x
Cynodon transvaalensis) and one of the more successful species is Wintergreen.
6
Table 2.2: Common turfgrass species and their tolerances to different environments
Latin Name Common Name
Warm or
Cool Season
Tolerances
References
Drought
Salt
pH
Wear
Recuperative
Pote
ntial
Heat
Cold
Frost
Mow
Shade
Flood
Agrostis canina Velvet bentgrass Cool P P P P G MG [9, 12-14]
Agrostis capillaris Colonial bentgrass, common
bentgrass, Highland bentgrass Cool P P
5.5-
6.5 P M M MG MG MG [8, 9, 12-17]
Agrostis stolonifera Creeping Bentgrass Cool P MG 5.5-6.5
P MG M G
G M G [8, 9, 12, 13,
15-17]
Anoxopus affinis Carpet grass Warm P P 4.5-
5.5 P M G P M M
[8, 9, 12-14, 16]
Buchloë dactyloides Buffalo grass Warm G M G G M P G [9, 12-14, 16,
17]
Cynodon dactylon Couch, bermudagrass Warm G G 5.5-
7.5 G G MG P MG P G [8, 9, 12-17]
Cynodon transvaalensis South African couch Warm G M MG [13, 15, 17]
Digitaria didactyla Blue couch, Queensland blue Warm G MG 5.5-
6.0 MG MG M P [8, 12]
Distichlis spicata Saltgrass Warm G [13, 16]
Eremochloa ophiuroides Centipedegrass, Chinese lawn
grass Warm P P
5.0-
6.0 P P G P M M P
[9, 12-14, 16, 17]
Festuca arundinacea Tall fescue Cool MG MG 4.7-
8.5 MG P MG M P G [8, 9, 12-17]
P = Poor, M = Moderate, MG = Moderate to Good, G = Good
7
Table 2.2 cont: Common turfgrass species and their tolerances to different environments
Latin Name Common Name Warm or
Cool Season
Tolerances
References
Drought
Salt
pH
Wear
Recuperative
Pote
ntial
Heat
Cold
Frost
Mow
Shade
Flood
Festuca longifolia Hard fescue Cool MG P G [9, 14, 16]
Festuca rubra Red fescue, Chewings fescue Cool MG M 5.5-
6.5 M M P M M G P [8, 9, 12-17]
Lolium multiflorum Annual ryegrass, Italian
ryegrass Cool P M
6.0-
7.0 P P
P
[9, 13, 15-17]
Lolium perenne Perennial ryegrass Cool M M M P P P M M P [8, 9, 13-17]
Paspalum notatum Bahiagrass Warm G P 6.5-
7.5 MG P P P M
[9, 13, 14, 16, 17]
Paspalum vaginatum
Paspalum distichum
Seashore paspalum, salt water
couch Warm G G M G P MG MG [8, 13-17]
Pennisetum clandestinium Kikuyu Warm G MG G MG [8, 12, 13, 15,
16]
P = Poor, M = Moderate, MG = Moderate to Good, G = Good
8
Table 2.2 cont: Common turfgrass species and their tolerances to different environments
Latin Name Common Name Warm or
Cool Season
Tolerances
References
Drought
Salt
pH
Wear
Recuperative
Pote
ntial
Heat
Cold
Frost
Mow
Shade
Flood
Poa annua Annual bluegrass, wintergrass Cool P 5.5-
6.5 P M MG G P [9, 13-17]
Poa pratensis Kentucky bluegrass Cool M P 6.0-
7.0 M MG M MG M M M
[8, 9, 13, 14, 16, 17]
Poa trivialis Rough bluegrass Cool P P 6.0-
7.0 P P G MG MG
[9, 13, 14, 16, 17]
Stenotaphrum secundatum St Augustinegrass Warm M G 6.5-
7.5 M MG G P P G
[8, 9, 13, 14, 16, 17]
Zoysia Japonica Japanese lawn grass,
zoysiagrass Warm G MG
6.0-
7.0 G G G M MG MG P
[8, 9, 13, 14, 16, 17]
Zoysia materella Fine-leaf zoysiagrass, manila
grass Warm G G
6.0-
7.0 G G G P MG MG P
[8, 9, 13, 14, 16, 17]
P = Poor, M = Moderate, MG = Moderate to Good, G = Good
9
Table 2.3: Rough ranking of colour loss of warm-season turfs during dormancy. Adapted from [8, 9,
18].
Most
discolouration
Eremochloa ophiuroides (centipedegrass)
Buchloë dactyloides (buffalograss)
Stenotaphrum variegatum (Variegated St. Augustinegrass)
Stenotaphrum secundatum (St. Augustinegrass)
Paspalum notatum (bahiagrass)
Pennisetum clandestinum (kikuyu)
Cynodon dactylon (couch)
Zoysia materella (manilagrass)
Zoysia japonica (Japanese lawngrass)
Least
discolouration
Cynodon dactylon x Cynodon transvaalensis (Tifway)
Paspalum vaginatum (Seashore paspalum)
Cool-season turfs may go dormant over the summer months or under drought-stress
[8]. However discoloration is generally not an issue. Some discoloration may occur over
winter, however this is not as severe as warm-season turfs.
Growth periods for warm- and cool-season turfs also vary significantly. Warm-season
grasses tend to grow during spring to early summer [8] and fertilization and access to
water is important during these times. During summer growth will drop off somewhat
and root growth is important in autumn prior to the turf becoming dormant. Cool-season
turfs grow in the opposite way, with autumn and spring being the main growth periods
with minimal growth over winter and many species going dormant over summer [8].
This in turn impacts on fertilization and water availability.
Other differences between warm- and cool-season turfs ultimately come done to impacts
of gameplay and safety. These issues are discussed in Sections 2.1.4 and 2.1.6
respectively.
2.1.2 Artificial turfs
Due to scientific advances and increasing water scarceness there has been an increase in
the use of artificial surfaces for sports fields. Third generation artificial turfs have
significantly improved in terms of visual impact and playability. The turfs currently
available consist of a perforated rubber base with the artificial blades attached. Over
this, to hold the blades upright is a layer of sand followed by a layer of rubber granules.
These granules are often made from recycled automotive tyres [19]. The granules can
also be dispersed during play and apparently can get into the eyes, nose and mouths of
players [19], though wetting prior to play would reduce this. The field would generally
need to be re-levelled after play [19].
The use of artificial turf does not necessarily eliminate the need for water however. Solar
heat is easily absorbed and where natural turfs can transpire (i.e. evaporate water)
lowering the surface temperature, this is not possible in artificial turfs. Some
experiments have shown the surface temperature to reach as high as 93 °C compared to
an air temperature of 37 °C [20], although about 20 °C higher than natural turfs appear
10
more common [19, 20]. This has two impacts, firstly it results in the dehydration of
players using the surface and potentially increase in heat-based injury from contact with
the surface. Secondly, it has the potential to increase the potential for injury due to
increasing traction [21]. To overcome these issues water is generally applied to the
surface of an artificial turf before play [19]. Irrigation has been shown to reduce the
surface temperatures by approximately 10 °C [20].
The application of water and potential for rain also bring about a second issue in runoff.
Typically water from an artificial turf should be collected and undergo some basic
treatment (e.g. detention) before release due to product that may leach from the
artificial turf, specifically polyaromatic hydrocarbons and zinc from the rubber infill [22,
23]. The content of these compounds emitted is proportional to the age of the field [23],
but in the early stages can be significant and the potential environmental impacts,
particularly from zinc, must be considered [23, 24].
Potential health impacts and injuries associated artificial turfs are discussed in Section
2.1.6, however it is important to remember that minor injuries such as abrasions and
burns do appear to be more significant on artificial turf while concussions appear less
likely to occur [25]. This increased risk of largely insignificant injury has led to changes
in player’s attitudes and perceptions towards artificial turf. The only study to date to look
at the impact of play in soccer has suggested that players take less risks and play a less
aggressive game on artificial turfs than natural turfs [26]. Specifically they are less likely
to use a sliding tackle due to the injuries they may sustain. This in turn impacts player
perceptions of a game played on artificial turfs, with respondents to a survey suggesting
that games played on artificial surfaces are worse than on natural turfs [26] though this
is not necessarily the case. Importantly, the study found that players that regularly use
an artificial surface adapt their game play to that surface and the impacts in these cases
can be fairly insignificant [26].
One final impact of artificial turfs on game play comes from the cushioning effect of the
rubber infill. Where a natural surface is quite hard, artificial surfaces are not an absorb
some of the energy used in running. While this was not found to affect the speeds
players achieved on the surface [26], it did result in players working harder to achieve
the same results and tiring quicker [27].
2.1.3 Soil
The soil that makes up the root zone will also influence water requirements. Soil is a
matrix of particles and aggregates of different size [28]. As the particles cannot pack
intimately close to one another, there are gaps and channels between them that are
generally referred to as pores. The size of these pores varies depending on soil
properties. Large particles like sand tend to have very large pore spaces while small
particles like clay have very fine pores. Clays can, however, aggregate. In doing this
smaller particles cling together to form larger particles. This leaves large pores between
the aggregates while small pores exist within the aggregates [28]. This is particularly
useful in soil for turf.
11
Table 2.4 Recommended maximum rate of irrigation for various soil classifications. Adapted from
[3]
Soil Type Application Rate
(L.hr-1.m-2)
Coarse sandy soil 50
Coarse sandy surface/compacted subsoil 44
Light sandy loam 44
Light sandy loam surface/compacted subsurface 31
Silty loam/compacted subsoil 15
Heavy textured clay 5
Different soils have different percolation rates and capacity to hold water. This is related
to the pore size. In general, large pores increase the percolation rate, while small pores
assist in the retention of moisture [28]. While sandy soils have high percolation rates,
they have poor soil retention qualities. Well-structured aggregated clay on the other
hand have both good percolation properties and good soil moisture retention [28]. While
the level of water retention will determine how much water is available for use,
percolation rates will limit the maximum irrigation rate. Table 2.4 shows the
recommended maximum rates for irrigation of a range of soils.
In general for a turf to grow a soil pores sizes in excess of 0.1 mm are required [28].
This is due to the size of the root and its ability to work its way through a soil as well as
having sufficient water and oxygen for growth. Fine soils, such as lake and flood plain
sediments are not suited for sport fields due to the smaller pore size resulting in poor
percolation and poor root growth [28].
Classifications of soils are based around the distribution of particle sizes within the soil.
Based on their size, particles are classified as either clay (<2 µ), silt (2-20 µ) or sand
(20-2000 µ) [29]. From these definitions it is possible to classify a soil texture using the
triangular graph found in [29]
There are two main soil moisture definitions that are important in irrigation. The first is
the field capacity. This is the amount of moisture retained in a soil after the excess has
drained away after irrigation or rainfall [28]. Ultimately this is the maximum amount of
water that can be retained by a soil. Table 2.5 gives the field capacity for different
classifications of soil. The second important definition is the permanent wilting point.
This is the soil moisture content from which the turf will stop extracting water. This
ultimately is the driest a soil should become prior to irrigation [28]. Typical ranges for
the permanent wilting point of various soils are also shown in Table 2.5.
12
Table 2.5 Field capacities and permanent wilting points for various soil types. Adapted from [30]
Soil Texture Class Field Capacity
(cm3.cm-3)
Permanent Wilting Point
(cm3.cm-3)
Sand 0.07 – 0.17 0.02 – 0.07
Loamy Sand 0.11 – 0.19 0.03 – 0.10
Sandy Loam 0.18 – 0.28 0.06 – 0.16
Loam 0.20 – 0.30 0.07 – 0.17
Silt Loam 0.22 – 0.36 0.09 – 0.21
Silt 0.28 – 0.36 0.12 – 0.22
Silty Clay Loam 0.30 – 0.37 0.17 – 0.24
Silty Clay 0.30 – 0.42 0.17 – 0.29
Clay 0.32 – 0.40 0.20 – 0.24
2.1.4 Requirements of Surfaces for Sports
The physical requirements of turf or other surfaces for various sports have been
investigated for about thirty years, but with the rise in artificial turf usage over the last
decade, guidelines or regulations for each sporting authority have only recently been
released. Table 2.6 outlines the current requirements for each sport. In the scientific
literature, the focus has been on characterising existing systems or investigating artificial
turfs. In general this means there is significant research on cool-season turfs, with
minimal work on warm-season turfs. The following sections summarize the current state
of knowledge.
2.1.4.1 Ball Bounce Resilience
Ball bounce resilience is defined as the ratio of the height a ball bounces compared to
the height dropped [31]. It is particularly important to sports such as cricket, tennis and
the football codes. Table 2.7 shows recommendations for ball bounce resilience from the
scientific literature. While it is somewhat dependent on turf type and turf quality the ball
bounce resilience is significantly influenced by soil type [31]. Studies by Canaway [32,
33] have shown that heavy soils give higher ball bounce resilience than sand under
normal conditions while the reverse occurs during and after wear. This was attributed to
the pooling of rainwater due to poorer infiltration of the soil by water during rain events.
This in turn significantly reduces the ball bounce resilience. Though it is not as significant
a factor, increasing mowing height was shown to decrease the ball bounce resilience, as
was increased plant biomass [34]. Table 2.8 gives the ball bounce resilience for a range
of turfs and soils.
13
Table 2.6 Turfgrass quality requirements as defined by sporting authorities
Characteristic Test Rugby Union
[35]
Hockey
[36]
Soccer (1 Star)
[37]
Soccer (2 Star)
[37]
Aussie Rules
[38]
Cricket
[38]
Vertical Ball Rebound
30-50% 5-20% 0.6-0.85m 0.6-1m 30-50% 5-20%
Angled Ball Behaviour
50-70% at 50
km/h with an
impact angle of
25o
45-60% 45-70% 45-70% 35-60%
Traction IRB
Method 30-50 Nm
25-50 Nm
15-25 Nm
spikes, 7-15
Nm
Energy Restitution
30-50%
Base permeability EN12616 > 180 mm/h > 150 mm/h 180 180
Ball Roll
5 - 15 m 4-8m 4-10m
Ball to Surface Friction
>= 0.5 static,
>= 0.35
dynamic
Underfoot Friction
0.6 - 1.0
Force Reduction
40-65% 60-70% 55-70%
Linear Friction - Stud
Deceleration 3-5.5 g 3-6 g
Linear Friction - Stud Slide
130-210 120-220
Rotational Resistance
30-45 Nm 25-50 Nm
14
Table 2.7 Recommendations for ball bounce resilience. Adapted from [31]
Sport Recommended Ball Bounce Resilience (%)
Soccer
20 – 45
25 – 38
20 – 50
Hockey 20 – 40
8 – 12
Tennis 25 – 36
Cricket 20 – 34
12 – 19
Table 2.8 Ball bounce resistance on different turfs and soils.
Species Soil Ball Bounce Resilience (%) Ref.
Bare ground Clay 41.4 [31]
Poa annua (Annual bluegrass) Sand 29.5 [32]
Soil 28.3 [32]
Lolium perenne (Perennial ryegrass) Sand 34.4 [32]
Soil 33.4 [32]
Poa pratensis (Kentucky bluegrass)
Sand 33 [32]
Soil 30.5 [32]
Clay 30.9 [31]
Festuca arundinacea (Tall fescue) Sand 34.7 [32]
Soil 36.5 [32]
Agrostis castellana (Browntop bentgrass) Sand 31.4 [32]
Soil 31.9 [32]
Agrostis stolonifera (creeping bentgrass) Clay 30.7 [31]
Festuca rubra (Chewing's fescue) Sand 35.2 [32]
Soil 35.8 [32]
Festuca rubra (Red fescue)
Sand 35.8 [32]
Soil 36 [32]
Clay 37 [31]
2.1.4.2 Rolling resistance.
The rolling resistance of the turf is ultimately the deceleration that the ball experiences.
It is defined as the distance the ball will roll across the surface before either stopping or
losing a certain proportion of its speed [31]. It is essentially a measure of the speed of
the turf and is important in sports such as golf, bowls, cricket, hockey and soccer. There
are a number of techniques to measure ball roll, but an important specification is that
the ball roll from a height of 1 m down a 45° incline [31]. The US Golf Association uses a
slightly different instrument called a ‘stimpmeter’ [31]. Bowls greens also use a different
technique, although the reproducibility is questionable [31]. When comparing data on
rolling resistance it is important to keep these differences in mind.
15
Table 2.8 Bowls green speed (in s) for different turfgrass species. Adapted from [39].
Species Dry Wet
Festuca rubra ssp. litoralis
(Slender red fescue) 11.5 11.5
Festuca rubra ssp. commutata (Chewing’s fescue)
10.9 10.8
Agrostis capillaris
(Colonial bentgrass) 10.9 10.7
Agrostis castellana
(Browntop bentgrass) 11.2 10.9
Poa annua
(Annual bluegrass) 10.5 10.2
Table 2.9. Golf green roll distance (in m) for different turfgrass species. Adapted from [39]
Species Dry Wet
Festuca rubra ssp. Litoralis (Slender red fescue)
2.21 1.90
Festuca rubra ssp. commutata (Chewing’s fescue)
2.10 1.82
Agrostis capillaris
(Colonial bentgrass) 2.10 1.80
Agrostis castellana
(Browntop bentgrass) 2.09 1.80
Poa annua
(Annual bluegrass) 1.72 1.51
Rolling resistance can be influenced by a number of factors. As would be expected taller
grass (higher mowing height) results in lesser roll [40]. While mowing height is
important, surface moisture also has a role to play, with wetter soils resulting in lesser
roll [40]. This would in turn imply that during periods of rain more pervious soils will
perform better under this parameter.
The effect of turf species is reasonably well defined [39]. Tables 2.8 and 2.9 give the ball
roll resistance for different bowls greens and golf greens. It should be noted that
although this data came from the same study, the measurement techniques were
different. Overall, however, this studied showed the best performance was with Festuca
rubra spp. litoralis (Slender red fuescue) [39]. An investigation of Cynodon species has
given roll distances greater than those reported in Table 2.9, typically in the range 2.34
to 2.94 m [41]. This may be due to differences in the ball roll test used however,
although the authors claim the coefficient of friction is similar to that seen for Agrostis
stolonifera. Importantly, the only difference within the Cynodon species was an apparent
decrease in the ball roll distance for South African couch (Cynodon transvaalensis).
16
2.1.4.3 Friction and Spin
While this property is very important to a turf surface, it is poorly understood. It is
essentially responsible for variations in speed, direction and ball rotation during ball-
surface contact. This is partially because it is difficult to define scientifically and this
leads to significant variation in the experiments that have been performed, though they
typically focus on what leads to friction and spin [31]. Consequently there has been no
significant work published on this property and its variation between different turfs.
2.1.4.4 Shoe-Surface Traction
Shoe-surface traction defined the grip of the shoe on a surface. While it may be an injury
risk (see Section 2.1.6), it is generally considered desirable to ensure best player
performance [21]. Ranges of “normal” traction ranges for Australian Football League
fields are shown in Table 2.11. In the unacceptably low range players are likely to slip
and the pace of the game slows, while in the unacceptably high range, the surface holds
too well and places significant stress on joints during pace and direction changes.
Measurement techniques for traction can vary, but a selection of studies by Canaway
[31-34] have established an apparatus to test the traction using a studded disc that
closely mimics the studs used in sports shoes. Table 2.12 shows the results of a range of
turf species and soil types. Traction values have also been determined for warm-season
species, while these are not directly comparable because of slight differences in
measuring technique, the ultimate source of resistance is similar and the values are in a
similar. These values are shown in Table 2.13.
Table 2.11 Acceptability of different traction values in AFL. Adapted from [42].
Performance Indicator Traction (Nm)
Unacceptably low < 20 Low normal 21 – 39 Preferred Range 40 – 55
High normal 55 – 74 Unacceptably high > 75
17
Table 2.12 Traction for different turf species on different soils.
Species Soil Traction
(Nm) Reference
Poa annua (Annual bluegrass) Sand 55 [34]
Soil 52 [34]
Lolium perenne (Perennial ryegrass)
Sand 72 [34]
Soil 66 [34]
Unspecified 66 [33]
Poa pratensis (Kentucky bluegrass)
Sand 72 [34]
Soil 70 [34]
Unspecified 77.6 [33]
Festuca arundinacea (Tall fescue) Sand 69 [34]
Soil 64 [34]
Agrostis castellana (Browntop bentgrass) Sand 66 [34]
Soil 57 [34]
Agrostis tenuis (Highland bentgrass) Unspecified 58.4 [33]
Festuca rubra (Chewing’s fescue) Sand 77 [34]
Soil 68 [34]
Festuca rubra (Red fescue) Sand 74 [34]
Soil 71 [34]
Festuca rubra (Highlight) Unspecified 55 [33]
Table 2.13 Average traction on warm-season turfs. Adapted from [43]
Turf Species Average peak torsion
(Nm)
Vegetative Bermudagrass (Cynodon dactylon) 75.5
Seeded Bermudagrass (excluding "Princess" and Riviera") (Cynodon dactylon)
66.4
Densely Seeded Bermudagrass - "Princess" and "Riviera" (Cynodon dactlyon)
76.7
Hybrid Bermudagrass (Cynodon dactylon x
transvaalensis) 75.3
Queensland blue couch (Digitaria didactyla) 69.6
Swazigrass (Digitaria didactyla) 82.3
Seashore Paspalum (Paspalum vaginatum) 64.9
Kikuyugrass (Pennisetum clandestinum) 55.7
St Augustinegrass (Stenotaphrum secundatum) 61.8
Marine Couch (Sporobolus virginicus) 48.9
Japanese lawngrass (Zoysia japonica) 65.1
Manilagrass (Zoysia matrella) 60.2
18
2.1.4.5 Surface Hardness
Surface hardness is important primarily from the point of view of safety (see Section
2.1.6). However it also impacts on the endurance of players during a match and its
speed [21]. While surfaces that are too hard can result in injuries to players, soft
surfaces are more elastic and absorb more energy from players during running. This in
turn means players are required to do more work for the same results and ultimately tire
quicker. This is one of the significant differences that has been seen by both researchers
and sportsmen with third generation artificial turfs [27, 44]. Here the rubber infill gives a
significant cushioning effect and causes players to work harder and tire quicker than on
natural turf surfaces [25]. Ultimately a good balance of safety and playability is required
when aiming for a specific surface hardness.
Surface hardness is primarily a factor of the underlying soil [21], however the cushioning
effect provided by some turfs can provide for some more subtle differences. A more
thorough discussion is provided in Section 2.1.6.
2.1.5 Management of Sports Turfs for Drought and Long Dry Spells
2.1.5.1 Management Practices
Mowing
There are a number of different viewpoints on how to use mowing height to reduce the
irrigation requirement of a field. Differences largely come about from the whether it is a
long-term or short-term view. Over the long-term, it is generally recommended that
mowing occur at the highest height allowed by the turf and users [4]. This allows the
roots to grow longer and ultimately gives the turf a greater drought resistance [45].
Once a drought or water-shortage has descended on the field, the mowing height can be
reduced. This will decrease the surface area of the leaves and give a short-term
decrease in evapotranspiration [8]. It should be noted however that this is more efficient
for cool-season turfs than warm-season [10]. This is due to the more horizontal nature
of leaves in warm-season turfs generally providing shading of the soil and lower leaves
[8]. Lower mowing heights ultimately only exposes lower leaves that previously had not
been transpiring at high rate.
Mowing frequency also impacts on water use, with increased frequency increasing
damage and therefore growth of the turf [8]. In drought conditions it is best to reduce
the mowing frequency where possible.
Fertilizer Use
The use of fertilizer encourages growth. This growth requires water and consequently the
evapotranspiration of a turf increases with fertilizer use [46]. Where it is feasible
fertilizer use should be reduced or avoided altogether in order to reduce irrigation
requirements. Alternatively, organic fertilizers can be employed that release nitrogen at
a slower rate reducing water requirements [3].
19
Other Practices
Other practices that can be useful in reducing water requirements include:
• Removal of thatch will improve water penetration to the soil and irrigation
efficiency [8].
• Aeration of turf should occur to reduce surface compaction and improve
percolation of water into the turf. Recommendations suggest this should occur
prior to irrigation or rainfall [3].
Finally, it will also be important for turf managers to consider how changing practices
and more intensive use will impact on turf wear. Often during water shortage activities
will be concentrated onto specific fields due to the water restrictions. Consequently the
following practices should be considered:
• Restrict training and pre-season matches to non-essential fields [3]
• Relocation of centreline and goal box in football to reduce wear in these areas [3]
• Widening of the wicket table in pitch based sports to wear in this area [3]
2.1.5.2 User Practices
There are a range of practices that can be adopted by users to reduce the effect of wear
and damage to a turf when it is under reduced irrigation conditions. These include:
• Transfer fitness and skills training off match or turf surfaces [3]
• Reduce playing time or shorten the season [3].
• For warm-season turfs consider altering the sporting season from a winter sport
to a summer sport [3]
• Rotate training areas when on the field [3]
• Don’t use studs on fields [3]
20
2.1.6 Sporting Injury, Health and Turf
2.1.6.1 Introduction
Injury is generally the most significant concern managers have when changing a turf
from one form to another. Understanding what can cause injury and what the main
differences could be is important when making a decision to change turf type. The
following section is a discussion of the properties of turf that increase injury rates as well
as the current state of the knowledge with regards to injury comparison between warm-
and cool-season turfs and natural and artificial turfs.
2.1.6.2 Properties that Cause Injury
A very thorough review of sports injuries has recently been performed by Chivers and
Orchard [21]. They felt there is little work to connect ground conditions to injury and
that the studies generally performed rely heavily on perceptions. However, they were
able to identify environmental hazards at sporting grounds that relate to injury. These
include:
• Uncovered hazards such as sprinkler heads or cricket pitches
• Uneven surfaces
• Debris, rubbish and rubble
• Type of surface (natural vs synthetic, clay vs sand)
• Poor turf coverage
• Type of grass
• Surface hardness (inversely proportional to soil moisture content [21])
• Surface traction (correlated to the amount and type of grass cover [21])
• Weather conditions
In general the hardness and traction are probably most significant as other issues, such
as the type of surface, type of grass and weather conditions are related back to these
two properties.
Early-Season Bias and Hardness
Injuries that are related to ground conditions are generally associated with the lower
extremities – legs, ankle, knees etc [21]. Most studies focus on these type of injuries, in
particular the ACL (Anterior Cruciate Ligament). Early studies into ground conditions and
injury focused on the phenomenon of early-season bias in sports injuries and most of the
available literature deals with this issue. Early-season bias refers to the increased rate of
injury seen in some sports at the start of a season. Researchers typically associate it
with ground hardness as the sports it is associated with are played during winter when
rainfall increases and evaporation decreases making a surface softer [21]. Evidence for
this is cited in the results of a study of American football where early-season bias was
only seen in open air fields, not indoor stadiums [21] and that American soccer, a
summer sport, shows a late season bias that would be associated with increasing
hardness as a surface dries out [47]. There is some controversy with this however as not
all sports show the same trends. While early-season bias is reported in rugby union [48],
American football, European soccer, Australian rugby league and Aussie Rules football
did not show a statistically significant early-season bias [21, 49, 50] and Gaelic football
instead saw a late-season bias [21]. There is also the possibility that early-season bias is
21
due to the fitness level of the players as they start a new season. Importantly, Orchard
[49] has shown a significant trend towards softer grounds that is accompanied by
increased injury, but statistically the two could not be related. The conclusions were that
while surface hardness may play a role, other factors, particularly traction may be more
significant.
Other studies have however identified hardness being related to injury in other ways. A
study of the AFL has shown that weather conditions are significantly associated with
injury risk [49]. In particular conditions of high evaporation for one month prior to the
match and low rainfall for the previous year were associated with higher injury risk. An
AFL study has also argued that greater hardness led to faster games being played on the
surface, lowering cushioning properties and increasing collision impact forces [21].
Traction
The importance of traction to sport injury is starting to receive significant attention, with
a number of researchers now highlighting it as having a major effect on injury risk. This
particularly refers to the surface-shoe interaction. A study in soccer [51] has shown that
high friction leads to the sportsman increasing loads associated with twisting and turning
during play. This, in turn, increases the injury rate. While surface hardness is related to
moisture and rainfall, causes for changes in traction are more difficult to identify, with
the obvious exception of high rainfall. Traction in general is related to the type of turf
cover and the extent of this cover. Studies have shown that traction shows a slow,
constant decline over a playing season [21]. Traction is also related to the mowing
height, with shorter cut grass giving higher traction values [52]. While high traction may
be a contributor to high injury risk, it is also highly desirable by sports participants and
some balance needs to be struck. Shoes used in most winter sports tend to increase
traction regardless of the surface type. While the type of surface may be a factor, the
design and manufacture of shoes may play a greater role in overcoming these issues
than turf choice [53].
2.1.6.3 Turf Type
Natural Turf
While grass type, in particular its relationship to surface-shoe traction, is believed to play
a role in injury risk, there is very little work investigating this as a variable. However, an
Australian AFL study has drawn the conclusion that the cool-season grass perennial
ryegrass has lower traction and is associated with lesser injury risk than the warm-
season turf couchgrass (bermudagrass) [49]. Similarly Kentucky bluegrass has been
shown to have higher traction than ryegrass and red fescue [52] and it is assumed will
be associated with greater injury risk as a result [48]. Result of studies into the shoe-
surface traction of various warm-season turfs are shown in Table 2.13 [43]. General
hypotheses about the effect of grass type on injury essentially consider the root density,
lower root and shoot density will lead to lower shoe-surface traction [8]. Mowing height
also plays a role in that greater mowing height gives greater cushioning effect and
therefore lesser injury risk [48]. Also traction has been found to increase as the mowing
height decreases.
22
Artificial Turfs
Research into injury risk on artificial turfs as opposed to natural turfs has shown varied
and sometimes contradictory results. This is due to the development of artificial turfs
from first generation Astroturf to the current third generation on which studies are just
starting to appear. The focus of this discussion will be on third generation artificial turfs
(the most likely to be installed now) and their impacts on injury rates and health.
Artificial turfs typically exhibit a higher traction than natural turf [4] and it would be
anticipated that a greater number of injuries would result. A large number of studies
however have not been able to conclusively show this with any difference between
artificial and synthetic not being statistically significant [54-58]. However, when a
breakdown of injury type is considered there is some variation witnessed. Foot and ankle
injuries have been found to be more common on artificial turf [54, 59]. Knee injuries are
typically considered only slightly more common on artificial turfs than natural [54, 58].
These results are complimented by the study of Nigg and Segesser [60] who found that
while non-serious injury is more common on artificial turfs, serious injuries occurred just
as frequently. In terms of non-serious injury, abrasions and burns are reported as being
typical and often missed in studies as they do not result in lost time [25]. While these
injuries are only of minor concern the potential for infection is quite important. A study
of American football players has shown a link between Staphylococcus aureus infection
and artificial turf burns with all abscesses forming at burn sites [61]. A further study was
able to show that players that experienced abrasions on artificial turf were seven times
more likely to suffer an infection than those who acquired their injuries on natural turf
[62]. Despite these observations however, it is still not certain how the infections are
transmitted or why the response on artificial turf is higher, although one suggestion has
been that soil microbes that help to decompose saliva, blood etc are not present in
artificial turfs [19].
Another important distinction is with concussions. Most recent studies have shown that
concussions resulting from head to surface collisions are less common on artificial
surfaces than natural surfaces [57]. This has been related to the extra cushioning effect
provided by the rubber infill used on artificial turfs [25] and is one of their primary
benefits.
The rubber infill while beneficial against injury, is also the cause for some concern with
regards to health impacts. The infill, and the turf itself, can release volatile components
as gases above the playing surfaces and be raised as fine dusts during sliding and
tackling [19]. These components are inhaled by players and have led to serious
concerns, particularly with respect to their cancer causing potential. The concern was so
great that in 2008 a number of state legislators in New Jersey, New York and Minnesota
have called for a moratorium to be placed on the installation of artificial fields using
recycled tyres as infill until further studies can be performed [63]. There is also a strong
grassroots movement in New York against the installation of further artificial turfs [64].
The major concerns here are with children being exposed to the chemicals as fields and
open spaces typically reserved for children are more likely to be replaced as a cost
cutting measure. A US EPA study however has suggested that the concentrations of
harmful compounds from infill were below dangerous levels and studies of the
bioaccessibility have suggested that there is no significant uptake when compared to
other sources [23, 63].
23
2.2 Irrigation Water
2.2.1 Introduction
The impacts of water for irrigation are numerous. One of the most import concepts to
understand however is the how to determine how much water to use or when and how
to add water. Signs of over-irrigation commonly generate complaints [65] and will be
even more significant during times of water shortage. The first part of this section looks
at irrigation modelling and the sensors and irrigation systems that exist that can help to
decrease water use and ensure over-irrigation does not occur.
Of equal importance is the effect of different irrigation water qualities on turf and soil.
This is important when considering diversifying water sources to ensure that the water
under consideration will not adversely impact on the play and quality of the turf.
2.2.2 Irrigation Volumes
2.2.2.1 Irrigation Modelling using Climatic Data
Irrigation modelling is important in understanding the requirements for a turf under
relatively realistic conditions. Water requirements can be estimated in a number of ways
the most basic being to subtract the rainfall for a site from the evaporation and assume
what remains is required as irrigation. This technique is a fairly poor estimate of water
requirements and is not particularly realistic. A more accurate way would be to consider
model water requirements on a daily basis based on previous years’ data. The way of
doing this is pictorially described in Figure 2.1. Ultimately, the soil acts as a reservoir of
water that is available to the turf. Rainfall will fill this reservoir until it is full and overflow
will occur, either as runoff or through percolation of the soil. The reservoir will be
depleted through use in the form of evapotranspiration (i.e. transpiration (or use) by the
turf in growth and evaporation from the soil). When the reservoir is depleted, extra
water must be added in the form of irrigation. The size of the reservoir is dependent on
the soil type and the type of growth required [4]. The evapotranspiration is dependent
on the turf type and the type of growth required (or available moisture) [4]. The ratio of
percolation to runoff is also dependent on soil type, but this is not particularly important
when calculating irrigation requirements.
The following section will provide a mathematical explanation of irrigation modelling
techniques.
24
Figure 2.1 Basic illustration of water balance in turf management: Descriptive model (above) and
engineering model (below)
Step 1 – Soil Water Retention
Determination of the ability of a soil to hold water is important to understanding the size
of the irrigation reservoir. This is dependent on two factors: (i) the soil type and (ii) the
root zone depth. The volume of water that can be depleted before irrigation is required is
given by the equation:
���,� � �� �� E-1
where VSM,C is soil’s moisture capacity, Rs is the soil retention factor and drz is the depth
of the root zone. Table <?> shows the soil retention factors for typical soil types for
different turf growth rates. The turf growth rates are important as they are determined
by the amount of available water in a turf. High growth will be seen where significant
water is available. Consequently the reservoir size for these soils is smaller as irrigation
should be triggered more regularly. Turfs that can have a lower growth rate have larger
reservoirs as the soil moisture content can be more heavily depleted. This results in less
frequent but larger irrigations.
The rootzone for a turf is affected by a number of properties including irrigation
frequency, frequency of fertilizer application and mowing height. In general for turfs the
rootzone depth is assumed to be on the order of 30 to 40 cm.
25
Table 2.14 Allowable soil moisture depletion (in mm.cm-1) for different soil textures under different
growth regimes. Adapted from [8]
Soil Type Vigorous
Growth
Strong
Growth
Good
Growth
Little
Growth
Minimum
Growth
Sand 0.3 0.4 0.5 0.6 0.6
Loamy Sand 0.4 0.6 0.7 0.8 0.9
Sandy Loam 0.6 1.0 1.1 1.2 1.3
Loam 0.9 1.5 1.7 1.8 2.0
Poor Structured Clay 0.5 0.8 1.0 1.1 1.3
Good Structured Clay 0.7 1.1 1.3 1.6 1.9
Step 2 – Determining Evapotranspiration
Evapotranspiration (ET) can be calculated through two main of techniques: the pan
evaporation model and the Penman-Monteith equation. The simplest of these is the pan
evaporation model.
The Pan Evaporation Method
The ET in pan evaporation is defined by the equation:
�� � �� � E-2
where ETc is the actual ET, EP is the evaporation from a flat water surface (or water pan)
and kc is the crop factor for the turf.
EP evaporation data can be obtained from the Bureau of Meteorology. Within Melbourne
there are three main sites measuring evaporation: Melbourne Airport, Melbourne Bureau
of Meteorology Head Office and Latrobe University at Bundoora.
Crop factors are dependent on the turf type and the amount of growth required. The last
of these is due to the fact that growth is dependent on water and greater growth will
therefore use greater water. Table 2.15 shows the crop factors for warm- and cool-
season turfs under different growth requirements. It is important that the growth
selected at this point is the same as that selected for soil moisture as ET is also
dependent on the amount of water available in the soil [66].
Table 2.15 Pan evaporation crop factors for warm- and cool-season turfs under different growth
conditions. Adapted from [8].
Turf Type Vigorous
Growth
Strong
Growth
Good
Growth
Little
Growth
Minimum
Growth
Warm-season 0.7 0.55 0.5 0.425 0.25
Cool-season 0.85 0.775 0.725 0.7 0.65
26
Penman-Monteith Equation
The FAO Penman-Monteith equation is more complicated than the pan evaporation
model, but does not require a knowledge of the local evaporation rate. It does, however,
require knowledge of some more complicated meteorological concepts. All the required
data is, however, available from the Bureau of Meteorology.
The ET by FAO Penman-Monteith is given by [67]:
�� � �.���∆�������� !!
"#$%&'$�()�(*�∆���+��.,�'$� E-3
Where ET0 is the reference ET, ∆ is the slope of the vapour pressure curve (kPa.°C-1), Rn
is the net radiation from the crop surface (MJ.m-2.day-1), G is the soil heat flux density
(MJ.m-2.day-1), γ is the psychrometric constant (kPa.°C-1), T is the mean daily air
temperature at 2 m height (°C), u2 is the wind speed at 2 m height (m.s-1), es is the
saturation vapour pressure (kPa) and ea is the actual vapour pressure (kPa).
The equation is essentially broken into two parts. The first part describes the water
evaporated through solar radiation and heat applied to the ground, the second describes
the equilibrium between water vapour (humidity) and water liquid above the grass and is
a function the wind speed.
In order to calculate the data above, a significant amount of information is needed. The
following discussion will break down how to calculate the individual components.
Psychrometric Constant (γ)
This is given by the equation [67]:
- � �.�/λ � 0.665 10�,5 E-4
Where P is the atmospheric pressure, cP is the specific heat (1.013x10-3 MJ.kg-1.°C-1), ε
is the ratio molecular weight of water vapour to dry air (0.622) and λ is the latent heat
of vapourization (2.45 MJ.kg-1).
Atmospheric pressure also needs to be calculated and can be found from the equation:
5 � 101.3 789,��.��:;�89, <;.8: E-5
Where z is the elevation above sea level (m).
Air Temperature (T)
For this term, the average of maximum and minimum temperatures is sufficient. This
data can be found from the Bureau of Meteorology.
Mean saturation vapour pressure (es)
The mean saturation vapour pressure can simply be taken as the average of the
saturation vapour pressure at the minimum and maximum temperatures. Each of these
can be found from the equation [67]:
=���� � 0.6108=7 ?%.$%""#$&%.&< E-6
27
where T is the maximum or minimum temperature (°C).
Slope of the saturation vapour pressure curve (Δ)
The slope of the saturation vapour pressure curve is calculated using the mean
temperature and the equation [67]:
∆ � ��9�@�.:+��(7 ?%.$%""#$&%.&<A�B�8,C.,�$ E-7
where T is the average temperature.
Actual vapour pressure (ea)
The term can be calculated in a number of ways, however, for the Melbourne area
calculation from relative humidity would be more appropriate due the relative ease with
which it can be obtained from the Bureau of Meteorology. The equation is defined as:
=D � �EFG*�+�� 7(!BF*H�(!BFI�
8 < E-8
Where RHmean is the average relative humidity, Tmax is the maximum temperature, and
Tmin is the minimum temperature.
Net Radiation (Rn)
The net radiation is a combination of the incoming shortwave radiation and the outgoing
longwave radiation. It is given by the equation [67]:
�J � �J� K �JL E-9
Where Rns is the net shortwave radiation and Rnl is the net longwave radiation.
Net Shortwave Radiation (Rns)
The Rns is given by [67]:
�J� � �1 K M��� E-10
Where Rs is the solar radiation and α is the canopy reflection coefficient and can be taken
as 0.23 [67].
Where solar radiation is not measured it can be calculated by [67]:
�� � 7N� O P� JQ< �D E-11
Where n is the actual duration of sunshine (h, available from Bureau of Meteorology), N
is the maximum possible duration of sunshine (h), Ra is the extraterrestrial radiation, as
can be taken as 0.75 and bs can be taken as 2x10-5z (where z is elevation above sea
level).
The extraterrestrial radiation can be calculated by the equation [67]:
�D � 8�:�R S����T� sinX sin Y O cosX cos Y sinT�� E-12
28
Where Gsc is the solar constant (0.082 MJ.m-2.min-1), dr is the inverse relative distance
between the Earth and the sun, ωs is the sunset hour angle (rad), φ is the latitude (rad)
and δ is the solar decimation (rad). The latitude can be estimated as -0.6603 for
Melbourne.
The inverse relative distance between the Earth and the sun is given by [67]:
� � 1 O 0.033 cos 7 8R,:; \< E-13
Where J is the day number (1= January 1st and 365 = December 31st)
The solar declination is given by [67]:
Y � 0.409 sin 7 8R,:; \ K 1.39< E-14
The sunset hour angle is given by [67]:
T� � cos�+�K tanX tan Y� E-15
Net Longwave Radiation (Rnl)
The net longwave radiation is given by [67]:
�JL � a 7BF*Hb �BFI�b8 < c0.34 K 0.14d=De 71.35 �)
�)f K 0.35< E-16
The temperatures in this case are given in Kelvin, σ is the Boltzmann constant
(4.903x10-9 MJ.K-4.m-2.day-1), ea is the actual vapour pressure (calculated through
equation E-8), Rs is the solar radiation (MJ.m-2.day-1) and Rso is the clear sky radiation
(MJ.m-2.day-1).
The clear sky radiation is the solar radiation assuming there is no cloud cover. It can be
approximated by the equation [67]:
��g � �0.75 O 2 10�;j��D E-17
Where Ra is the extraterrestrial radiation (calculated from equation E-12) and z is the
elevation above sea level (m).
Soil Heat Flux (G)
For daily calculations, this can be assumed as 0 [67].
Wind speed at two metres above ground level (u2)
The wind speeds are generally calculated by the Bureau of Meteorology at a height of 10
m above ground level. To convert this to 2 m wind speeds the following equation can be
used [67]:
k8 � k� �.�Clm�:C.���;.�8� E-18
Where uz is the wind speed at a height above the ground of z (in m).
29
The evapotranspiration calculated using the FAO Penman-Monteith equation has been
calculated for an artificial reference crop. This will need to be converted to
evapotranspiration for the turf using the equation:
�� � n� �� E-19
Where Kc is a crop coefficient, but does not take the same value as that for the pan
evaporation method. In general the Kc values for warm-season turfs can be taken as
0.85, while that for cool-season turfs can be taken as 0.95 [67].
Pan Evaporation vs. NAO Penman-Monteith
Calculations have been performed for ET from a warm-season turf near Melbourne
Airport, assuming its data. A comparison of the two estimations are shown in Figure 2.2.
From here it is quickly obvious that the Penman-Monteith model is significantly higher in
its ET prediction. This could simply be a function of the crop coefficients recommended
and used as the same general trends are seen. It is important to understand, however,
that the two cannot be used interchangeably.
Figure 2.2 Comparison of Penman-Monteith calculations to the pan evaporation model for a field
near Melbourne Airport.
30
Step 3 – Water Balance
With an understanding of the size of the reservoir, the inflow of water (rainfall, obtained
from the Bureau of Meteorology) and the extraction of water (evapotransipiration), a
simple water balance can be performed. For each day the following calculation is
performed:
��� � ����+ O 5 K �o K �� O p E-20
Where VSM is the volume of available soil moisture, VSM-1 is the volume of available soil
moisture the previous day, P is the precipitation, ETc is the evapotranspiration calculated
for that day, ESM is the excess soil moisture and I is the irrigation depth. All values are
give in mm. Excess soil moisture can be determined simply as the water in excess of the
soil’s storage capacity. Irrigation is determined to be equal to the amount required to
saturate the soil (fill the reservoir) when the value for VSM drops below zero.
The actual volume for irrigation can then be determined by taking the following
equation:
�q�� � rstIGuv+�/Iww E-21
Where Virr is the irrigation volume in kL, I is the irrigation depth in mm, Afield is the area
of the field in ha and εirr is the irrigation efficiency. This is typically estimated as 0.75
[4]. However the Queensland Water Commission has estimated irrigation efficiencies for
a range of irrigation types. These are shown in Table 2.16. The values should only be
used as a guide to general trends however as there are significant differences within
irrigation systems due to differences in user practices and uniformity.
By performing this calculation over an extensive period (at least one year, preferably
more), an average annual irrigation requirement for a field can be determined that is
more accurate than simple calculations based on annual rainfall and evaporation. It is
also possible to determine daily requirements by updating this model based on daily ET
and rainfall figures in order to estimate when irrigation may be required.
Table 2.16 The Queensland Water Commission guide to irrigation system efficiencies [68].
Irrigation System Soil Type
Clay Loam Sand
Drip 0.95 0.95 0.95
Microspray 0.5 0.5 0.55
Spray – Day 0.5 0.5 0.6
Spray – Night 0.55 0.6 0.65
Sprinkler – Day 0.65 0.65 0.65
Sprinkler – Night 0.75 0.75 0.75
31
2.2.2.2 Soil Moisture Sensors
A more accurate determination of irrigation frequency can be determined by directly
measuring the soil moisture content. Moisture sensors are mature technologies and a
number of different measurement techniques can be found in commercially available
technology [4]. The following techniques are commonly used:
• Neutron Gauges – This uses a radioactive isotope to generate neutrons for
probing soils and is considered the most accurate method for determining soil
moisture content [69]. The offset position of the calibration curve is significantly
impacted by changes in soil composition (due to neutron interactions with
individual isotopes) and must be calibrated to a soil before use [69]. The use of a
radioactive source will place strict regulations on its sale and use, meaning it
cannot be left unattended [69] and is probably unsuited for determination of
irrigation scheduling on sportsfields.
• Water tension – Also known as soil water suction or soil water potential, this is a
measure of the amount of energy with which water is held in a soil. It is
measured using a water-filled tube with a ceramic tip on one end and a vacuum
gauge on the other. The water in the tube comes to equilibrium with the
surrounding soil and the pull on the water is measured by the vacuum gauge
[70]. Measurements are generally dependent on soil type and the technique
needs calibration [70].
• Dielectric properties – These are probably the more common of the commercially
available soil moisture sensors [71]. Broadly they work around measuring
variation in the soil dielectric constant [71]. This is a function of water content in
the soil. There are two main types of dielectric sensors: Frequency Domain
Reflectometers (FDR) and Time Domain Reflectometers (TDR) [71]. The main
difference between the two is generally in their measurement technique. Their
accuracy is generally considered to be good with one study showing that FDRs
can be more accurate than neutron probes [69]. Capacitance-based sensors are
easily automated [72]. Importantly they are not affected by salinity or
temperature changes, but can be negatively impacted by bulk density changes
due to soil compaction [73].
• Electrical resistance – These sensors use gypsum blocks with pores sizes roughly
on the same scale as pores in the surrounding soil [69]. As such they are highly
dependent on the soil type. The electrical resistance is measured and this is a
function of water content. The technique is also sensitive to the salinity of the
soil moisture as this impacts on the conductivity readings. The gypsum can also
dissolve in high salinity water or in soils with a high moisture content [69].
Measurement error was found to be 20% or greater [69]. This can make them
more erratic than dielectric sensors [74].
• Heat Dissipation – This sensor uses a similar gypsum block to electrical
resistance measurements, but instead looks at the temperature rise due to
applied heat [69]. It has been shown to be unaffected by the soil temperature,
soil texture and salinity [69]. Though no claims have been made it is likely suffer
from the same dissolution problems of the electrical resistance meters. One
comparative study of soil moisture sensors found the results from the heat
dissipation sensor to be the most erratic and unreliable of the sensors used [74].
It was acknowledged that this could have been a result of the nature of the tests
however.
32
It is important that the installation of moisture sensors is performed correctly, as this
can impact on the final effectiveness of the techniques. Some reports have shown that
pockets of dry soil can leave sensors unresponsive to soil moisture changes [73]. Overall
it must be remembered that, like any sampling technique, the choice of location of
sensor is important in determining how representative it is of the overall turf conditions
[4]. This can be somewhat overcome by using multiple sensors [75], however this
comes with increased financial costs.
Calibration of sensors is also important, particularly as variations in soil-type can bring
very significant differences in response [70, 74]. Having said this a recent study has
shown the “out of the box,” uncalibrated sensors can still give responses that are
consistent enough for irrigation scheduling, despite the fact the actual values themselves
are no reliable [71].
Overall, the use of soil moisture sensors can make irrigation scheduling more accurate
than weather-based model predictions [4]. This in turn improves environmental
performance by decreasing the amount of nutrient leaching in runoff and to ground
water, particularly is high soils with a high percolation rate [71, 73].
2.2.3 Irrigation Delivery
When estimating irrigation requirements and investigating water savings, it is important
to understand the method by water is delivered to the soil. Looking at equation E-21, the
irrigation efficiency can have a significant impact on the amount of water required for
irrigation. Another significant factor is the uniformity of the delivery as this directly
impacts turfgrass quality [4]. In turf irrigation there are three main techniques that can
be considered: spray irrigation, subsurface drip irrigation and subirrigation.
2.2.3.1 Spray/Sprinkler Irrigation
The conventional technique for delivery of irrigation water to turfs remains sprinkler
irrigation [4]. This is due primarily to its simplicity, reliability and comparative low capital
costs. There are three main sprinkler irrigation techniques that are used:
• Irrigation through a portable sprinkler – This is an inexpensive option, but
requires significant labour costs. It has also been noted that the sprinklers can
be a target for theft [4].
• Quick coupling valves – This is in the intermediate range in terms of expense,
but still requires some labour. Importantly irrigation using this technique is often
inefficient [4].
• Automatic pop-up sprinklers – These require little labour, but can be quite
expensive. Where designed correctly uniformity and efficiency can be quite high
[4].
Irrigation using sprinklers has the benefit not only of being well established and
understood, but also can easily be monitored visually, something that is missing from
subsurface irrigation techniques [65]. The more expensive sprinklers are also more
easily automated and a general rule of thumb for efficiency is that greater automation
brings greater efficiency [4].
There are significant drawback from sprinkler irrigation however – the most significant
being the uniformity of irrigation. In general the radial (or circular) precipitation from a
33
sprinkler means that irrigation near the sprinkler head is generally more intensive than
irrigation at a greater distance, simply due to the larger area the water must cover [4].
To improve uniformity considerable overlapping is generally required. The suggestion
has been that using a triangular pattern gives a reasonable uniformity for greatest cost
effectiveness [4]. The pressure applied will also influence uniformity with low pressures
generally creating a donut pattern with more water delivery to the extremities than the
centre and high pressures giving greater irrigation in the centre than the extremities [4].
Careful selection of pressure and pipework that can influence pressure is a must.
Another drawback is the influence of wind and evaporation [4]. High winds can
significantly interfere with uniformity and also increase the rate of evaporation. Drop size
is also an important characteristic. Small droplets lead to greater evaporative losses, but
large droplets can be damaging to the turf and soil [8].
While sprinkler irrigation can still deliver the required volume of water for irrigation even
if at low efficiency the way in which it is delivered can have unintended effects.
Specifically, by applying water to the surface, the roots of turf tend to be smaller [45],
particularly where irrigation is fairly regular [8]. This decreases the drought tolerance of
the field as roots are unable to tap into deeper water reserves [45]. Reducing the
frequency of surface irrigation is one way of reducing this effect and ensuring adequate
rooting of turfgrasses [8].
Overwatering and runoff are also significant problems in sprinkler irrigation [65],
particularly with high labour techniques [4]. Runoff is a particular concern to local
councils during water restrictions as this is a visible sign of wastage to local residents
and can generate increased complaints [65]. The reason for this can often be due to the
rate of precipitation from the sprinkler (i.e. the rate at which water is applied). Where
this exceeds the rate of percolation through the soil, runoff and ponding become more
common. The selection of a sprinkler with a precipitation rate lower than the percolation
rate should help reduce runoff and ponding [4].
Energy use also tends to be higher as extra pumps are required at many sites in order to
regulate the pressure supplied [76]. This can be decreased somewhat though the use of
variable speed pumps that can allow for the optimization of pressure requirements for
irrigation on a regular basis [4].
2.2.3.2 Subsurface Drip Irrigation
Subsurface drip irrigation (SDI) applies water directly to the rootzone through the use of
porous pipes or drip tapes with inbuilt emitters. The emitters are often designed for
specific flow rates and developed in such a way as to ensure turbulence and minimise
blocking [77]. Where the system has been well designed, the distribution uniformity of
irrigation should be better than for spray irrigation [76, 78] and this is one of its most
important benefits. It should be noted that the design of these systems is highly
dependent on soil type and it permeability [79, 80]. While sand is well suited to SDI,
clay requires a more dense system due to issues with distribution [80].
It is generally assumed that SDI is more water efficient and produces less runoff than
spray irrigation, however there much scientific debate about this [81]. While the effect
crop growth is generally undisputed (subsurface irrigation either reduces water
requirements or significantly increase yields [76, 81]) the effect for turfgrass seems less
34
pronounced [81]. While some studies specifically on subsurface turfgrass irrigation that
have shown a decrease in water use (although this was not quantified) [65, 78], another
more thorough study showed that the difference in irrigation application between SDI
and sprinklers was negligible (465 mm for SDI versus 472 mm for sprinklers) [82].
Runoff and percolation issues have been shown to be reduced [65, 83] with one noting
the number of complaints lodged for water-runoff at a university were zero, compared to
six complaints for spray irrigation over a one year period [65]. Reduced runoff and
percolation in turn improves the environmental performance of irrigation with less
nutrients washing out after fertilizer application [78].
SDI also provides an opportunity to add nutrients directly to the rootzone. This has been
found to increase efficiency of use, particularly for phosphates [81]. The lower leaching
losses in turn contribute to improved environmental performance [83].
Other advantages of SDI include:
• Better weed management – by providing water only to the rootzone, germination
of seeds cannot occur unless rainfall is significant [78, 81].
• Safer application of lower quality waters – in the case of irrigation with recycled
water, lower qualities can be used due to the lack of contact between the water
and users [5, 78]
• Decreased energy costs – this is due to the lower pressure requirements of SDI
when compared to spray irrigation [78, 81]. These savings are more likely to be
realised where pumping is provided onsite, such as for stored water or where the
pressure from the potable water supply needs to be supplemented [65].
• Irrigation can occur at any time – this is important for fields under heavy use or
in areas affected by winds [76, 81].
• Decreased maintenance – this is generally claimed as being due to the lower
number of mechanical parts in the system and has been documented in some
cases [65, 78]. The downside is that when maintenance does occur, it is more
time consuming and expensive [81].
There are however disadvantages to the use of SDI, the most significant being emitter
clogging. This can occur in a number of ways: (i) root intrusion, (ii) chemical
precipitation and biofouling, (iii) soil clogging. Root intrusion has been documented in a
range of studies [65, 81, 82, 84] and is the main cause for concern particularly for
nutrient rich wastewater irrigation [85], however there are ways of avoiding it. Zoldoske
found that irrigation systems that incorporated a herbicide into the plastic were highly
resistant to root intrusion [65]. This technology is almost standard with the incorporation
of Treflan into emitters becoming relatively common [86]. It is also possible to add a
small amount of herbicide to the irrigation water to reduce root growth in the area of the
emitter [76]. Another suggestion has been to use a high frequency of irrigation to
produce a permanently saturated zone around the emitter to discourage root growth
[76].
35
Table 2.17 Recommended water qualities for use in subsurface drip irrigation. Adapted from [5, 76,
87].
Parameter Level of concern
Low Moderate High
pH < 7.0 7 - 8 > 8.0 Bicarbonate (HCO3, meq.L
-1) < 2 > 2 > 2
Iron (mg.L-1) < 0.2 0.2 – 1.5 > 1.5 Manganese (mg.L-1) < 0.1 0.1 – 1.5 > 1.5 Hydrogen Sulphide (mg.L-1) < 0.2 0.2 – 2.0 > 2.0 Total Dissolved Solids (mg.L-1) < 500 500 – 2000 > 2000
Suspended Solids (mg.L-1) < 50 50 – 100 > 100 Phosphate (mg.L-1) < 0.05 0.05 – 0.2 > 0.2
Chemical precipitation typically takes the form of iron, manganese or calcium salts [76].
Iron, manganese and phosphorus can also contribute to biofouling [5, 76]. Filtration of
irrigation water should occur prior to use and will decrease this somewhat [76]. Chemical
precipitation may still occur however and Table 2.17 contains the recommendations of
Harris [76, 87] and the Australian Guidelines for Recycled Water [5] with regards to
minimum water quality requirements for irrigation systems. These recommendations are
also effective against some biological growth. Alternatively small concentrations (0.5 to 1
mg.L-1) of a biocide such a chlorine may be able to reduce biofouling [87], though it
should be ensured it is kept low due to its potential toxicity to turfgrasses [16].
Soil clogging is a particular concern during shut down of the irrigation system when a
vacuum may form and potentially draw soil particles into the emitters [81]. This issue is
best dealt with by utilizing best design principles and ensuring that air and vacuum
release valve are appropriately placed in the system [76, 81].
Another significant limitation that is related to clogging issues is the ease with which the
irrigation system can be monitored [65, 76, 78, 81]. While spray irrigation can be
monitored visually for problems this is not the case for SDI. Instead secondary
techniques including monitoring pressures and flows must be used [65, 81]. This can
make it difficult to isolate a problem, and, as noted previously, where clogging occurs
maintenance costs can be significant [81].
Salt accumulation is also cited as a point of concern in SDI systems, particularly where
alternatively waters are used [79, 80, 84]. Where rainfall is insufficient to move salt
from the rootzone growth may be impaired and SDI may not be suitable.
Another drawback is where a turf has overseeding requirements. For seed germination,
water is generally required at the surface of the soil. While it is possible to design SDI
systems is such a way [81] it is generally always supplemented by spray irrigation [76,
81]. This can be efficient during establishment of turfs, however if it is required annually
for overseeding, SDI may not be suitable.
For more information of SDI, the Queensland Government Department of Primary
Industries and Fisheries have a series of short reports about design and management of
such systems [76, 77, 87-90].
36
2.2.3.3 Subirrigation
Subirrigation is the practice of artificially raising the water table to ensure water
available to a turf, without exposing it to potential evaporation in the atmosphere. The
water is stored below the root zone and is drawn up to the roots via capillary action [91].
Subirrigation systems essentially a large impervious lining (or pan) that is placed below
the root zone and criss-crossed with perforated pipes that perform the job of water
delivery and drainage [91]. This means that uniformity of irrigation is significantly higher
than in sprinkler systems [1]. An overflow pipe ensures the artificial water table does not
rise too far and waterlog the root zone.
At first glance the technique does not appear to be a water saving idea, however this is
not the case [91]. Once the water reserve has been established, water use can be quite
low. While the turf gets the water it needs, the capillary action limits the amount of
water in the root zone and particularly at the surface reducing evaporative losses. This
lack of water in the root zone also means that when rain falls there is less runoff and the
rainfall can be utilized efficiently as the soil still has storage capacity [45]. Percolation
losses are also reduced by the technique. Overall, water savings of 40-95% over
sprinkler irrigation have been reported using subirrigation [1]. This is complemented by
more extensive root growth that ultimately make a turf watered in this way more
drought tolerant [45].
Due to its location below the root zone, subirrigation does not suffer from the root
intrusion issues seen in SDI. Wilting of cool-season turfs commonly seen in spray
irrigation, has not seen in subirrigated turfs [92].
Subirrigation can be performed in two ways, by maintaining a level water table or using
a fluctuating water table. Krans showed a stable water table resulted in poorer yields
when compared to both fluctuating water tables and sprinkler irrigation making this the
more suitable technique [92].
The disadvantages of the technique are similar to those seen in SDI: capital investment
is significant; maintenance, though less regular, can be costly when required; and
monitoring can only be performed through secondary techniques [1]. The other
significant disadvantage is the potential loss of pigmentation of the turf due to low
dissolved oxygen content in the water [92]. While this was reported in older studies , it
has not been in more recent ones [45], suggestion some of the problems with the
technique have been overcome.
2.2.4 Storage Considerations
When considering using an alternative water source, it is important to consider how the
water will be stored. Often water is available at a constant rate, such as in decentralized
recycled water systems and sewer mining, or it is available when it is not needed. Under
these conditions storage volumes will determine the reliability of the system. The
material used to construct the storage will potentially impact the quality of the water.
The three main water storage techniques used are water tanks, artificial ponds and lakes
and aquifer recharge. Each of these is described below.
37
2.2.4.1 Tanks
Tanks are useful for storing water but typically are only economical on a small scale, due
to the amount of metal or plastic that goes into the construction of the tanks. Cost
estimates can be made using the equation (adapted from [93]):
x � 19.394��.��C, E-22
Where V is the volume in litres and C is the cost in Australian dollars. While tanks in the
kL range are affordable, ML sized tanks can become quite expensive.
The benefit of using tanks is that they are separated from the surrounding environment.
This prevents evaporation of the stored water while also preventing the contamination
from outside water. This is not to say that the water will not undergo some quality
changes. Rain water tanks can be rich in microbes that, while it may at first seem a
problem, appear to actually improve water quality [94]. On the other hand, the materials
used to make the tank can corrode and leach into the stored water if it is too soft or the
water is acidic [95]. Of particular concern are galvanised steel and copper components
that can leach zinc and copper into the stored water [96, 97]. If the concentration of
either of these species is too high it is particularly detrimental to the health of the turf
[8]. Iron may also leach from steel based tanks, however at low levels of application iron
has been found to be beneficial to turf in an irrigation water [9].
2.2.4.2 Artificial Ponds and Lakes
After a water has been treated, it should be of a suitable quality for storage in an
artificial pond or lake. If the land is available this could be a less expensive option
storage of large volumes of water. Another benefit of artificial lakes is the increased
amenity and visual aspects of the storage. Storages designed to mimic natural conditions
can lead to an increase to biodiversity in the area making the lake more pleasing to the
general public, and potential create a useful open space for the local community.
Increased biodiversity can also help reduce pests such as mosquitoes in the more
stagnant water [98], particularly over the longer periods of water accumulation (typically
winter). There is a potential negative from the increased biodiversity however in that
contamination of the water from animal faeces becomes a potential water quality issue,
both in terms of chemistry and biology. Artificial lakes are also more susceptible to
environmental conditions in that evaporation will concentrate the water. This can
possibly leads to cyanobacterial or algal blooms that will significantly impact the use of
the water. Cyanobacteria will release toxins into the water preventing its use, while
algae may release compounds such as surfactant that could influence the biology of soils
that are irrigated using the water and ultimately impact on the nutrient uptake of the
turf [16].
2.2.4.3 Aquifer Recharge
Aquifer recharge is another option for large volumes of water, where an aquifer is
available. Storage in an aquifer helps to reduce the footprint of the storage making it
more suitable where land area is an issue. It also means that environmental conditions
will limit water losses with only exfiltration from the storage rather than evaporation an
significant issue.
38
A secondary benefit comes from the long residence time and the loss of bacterial and
viral contamination as a result. Studies of aquifer storage systems worldwide have
shown highly efficient removal for Campylobacter (typical > 6 log reduction) and some
removal efficiency for rotavirus and Cryptosporidium depending on residence time in the
aquifer [99]. This is generally accompanied by changes in water chemistry, typically
from leaching of geological materials [100]. This can result in a decrease in pH of the
stored water [101]. The aquifer may also provide a small amount of nutrient reduction
due to the presence of a subsurface microbial colony surrounding the injection site
[100]. Organic compounds may also be transformed by similar processes. This will work
best where the injection site is separate from the extraction site. The changes in water
chemistry, particularly the loss of oxygen and increased mineral content, means that
treatment may be required upon abstraction from the aquifer. This may simply be
aeration [99] or other treatments common to groundwater. More information on
groundwater treatment may be found in Section 3.6.3.
2.2.5 Turf and Soil Health
2.2.5.1 Introduction
Changing the source of n irrigation water can potentially have adverse impacts on the
turf and soil quality. Negative impacts from toxicity, soil hydrophobicity and compaction
are just some of the conditions that need to be avoided. The following is a general
discussion of general water quality impacts.
2.2.5.2 Salinity
Salinity is probably the most pressing concern in the use of alternative water supplies. It
can have severe negative impacts on both soil and turf quality. In general salinity refers
to sodium ion content and to a lesser degree chloride ion content. However, it is often
the ratio of sodium to other ions, particularly calcium and magnesium, that can
determine its detrimental effects. This is due to the replacement of calcium and
magnesium in soils with sodium where its concentration is high. This in general leads to
structural changes in the soil, compaction and a loss in permeability for water making it
harder to irrigate [102]. In extreme cases the loss in permeability can prevent oxygen
transfer in the soil leading to the development of anaerobic zones and ultimately turf
death. This is exacerbated on sportsgrounds where a high volume of traffic is common
[16]. Saline toxicity comes in a number of forms and symptoms of saline stress will vary.
Harvandi and Marcum have outlined the symptoms at various levels of stress [103]:
• Early stages: blue-green or light, bright green coloration coupled with irregular
shoot growth
• Middle stages: blades increasingly wilted and darker green
• High salinity stress: burning of leaf tips, gradually extending down the length of
the blade. Root zones are shallow and growth stunted.
• Extreme salinity stress: growth minimal, shoot density decreases, turf death.
39
Table 2.18 Maximum salinity tolerance for various turfgrass species. Adapted from [13]
Species Salinity Tolerance
Distichlis spicata (seashore saltgrass) 35 dS.m
-1
Sporobolus virginicus (marine couch)
Paspalum vaginatum (seashore paspalum)
25 dS.m-1
Zoysia matrella (manilagrass)
Zoysia pacifica (goudswaard)
Puccinellia spp. (alkaligrass)
Zoysia japonica (Japanese lawngrass) 14 dS.m-1
Pennisetum clandestinum (kikuyugrass) 12 dS.m-1
Agrostis stolonifera (creeping bentgrass) 10 dS.m-1
Festuca arundinacea (tall fescue) 8 dS.m-1
Buchloe dactyloides (buffalograss)
7 dS.m-1
Lolium perenne (perennial ryegrass)
Agropyron cristatum (crested wheatgrass)
Festuca rubra (red fescue) 6 dS.m-1
Bouteloua spp. (grama)
5 dS.m-1
Bromus inermis
Lolium multiflorum (Italian ryegrass)
Poa pratensis (kentucky bluegrass) 4 dS.m-1
Anoxopus spp. (carpetgrass)
3 dS.m-1
Eremochloa ophiuroides (centipedegrass)
Paspalum notatum (bahiagrass)
Festuca brevipila (hard fescue)
Festuca ovina (sheep fescue)
Agrostis capillaris (colonial bentgrass)
2 dS.m-1
Agrostis canina (velvet bentgrass)
Agrostis gigantea (redtop bentgrass)
Poa trivialis (rough bluegrass)
Poa annua (annual bluegrass)
To avoid these conditions a general recommendation has been made to keep irrigation
water conductivity below 3000 µS.cm-1 as a minimum and preferably below 700 µS.cm-1
[102]. In general this type of salinity stress is considered more of an issue than sodium
or chloride ion toxicity as turfgrasses are generally more tolerant of this [102] although
it is highly species dependent. Table 2.18 provides a list of the salinity tolerances for a
range of turf species. Soil type also plays a role however with clays at greater risk than
sand. Highly saline waters are generally only recommended for irrigation of sandy soil
for this reason [16]. The ANZ guidelines provide limits for couch grown on various soil
types. It recommends conductivity values for irrigation water of 10800 µS.cm-1 on sand,
6100 µS.cm-1 on loam and 3600 µS.cm-1 on clay.
A more detailed way of determining the likelihood of salinity stress is to investigate the
sodium adsorption ratio (SAR). The SAR is defined mathematically as [8]:
40
Table 2.19 Recommended SAR and conductivity values for the protection of soils. Adapted from
[16].
Degree of Problem
Negligible Slight to
Moderate Severe
if SAR = 0 to 3 and EC > 0.7 0.7 - 0.2 < 0.2
if SAR = 3 to 6 and EC > 1.2 1.2 - 0.3 < 0.3
if SAR = 6 to 12 and EC > 1.9 1.9 - 0.5 < 0.5
if SAR = 12 to 20 and EC > 2.9 2.9 - 1.3 < 1.3
if SAR = 20 to 40 and EC > 5.0 5.0 - 2.9 < 2.9
yz� � QD#{|*$# #}~$#
$ E-23
where Na+, Ca2+ and Mg2+ are the concentration in meq.L-1. The SAR can be analysed
with the electrical conductivity of the irrigation water according to Table 2.19 to
determine likely effects. This should help maintain water permeability in the soil [16]. If
the SAR is too high, it is possible to add lime to the soil or irrigation water to improve
the water quality for irrigation. This is a common practice with recycled water in the
United States.
As mentioned previously specific ion toxicity is likely to be an issue only in rare cases.
While limits of 70 mg.L-1 have been set to ensure no effects of sodium toxicity, no levels
with severe effects have been recorded. It is also generally recommended that chloride
be maintained below 70 mg.L-1 or below 355 mg.L-1 to avoid any serious effects of
toxicity [16].
2.2.5.3 Boron
Boron is an essential trace nutrient for plantlife [8, 104], however high uptake of boron
by plants can also lead to toxicity. Boron toxicity is considered a major issue in plants
irrigated with a high boron water or grown on a high boron content soil. Boron toxicity
typically stunts the growth of plants and can lead to spot formation of leaves that
become necrotic. In turfgrasses boron will concentrate near the tips of blades and
necrosis occurs here [104].
Boron can become an issue with some water sources, particularly seawater and recycled
water. Desalination of seawater is typically performed by the reverse osmosis technique.
While this is relatively efficient at removing most salts, it is less efficient for removing
boron (about 30-40% is removed [105]). The result can be a relatively high boron
content in the product water. Boron can also enter recycled water streams through
boron-containing soaps and detergents, although the content is generally considered low
[16].
41
Table 2.20 Relative boron tolerance of six turfgrass species. Adapted from [104]
Most Boron Tolerant Cynodon dactylon (bermudagrass)
Zoysia japonica (Japanese lawn grass)
Poa pratensis (Kentucky bluegrass)
Festuca arundinacea (Tall fescue)
Lolium perenne (Perennial ryegrass)
Least Boron tolerant Agrostis stolonifera (creeping bentgrass)
Compared to other plant species, turfgrasses are quite tolerant to boron levels [104].
Different turf species are also more tolerant than others. Table 2.20 gives the relative
boron tolerances of six turfgrasses. While the Australian and New Zealand Guidelines for
Marine and Fresh Water Quality state boron levels in irrigation water should be
maintained below 0.5 mg.L-1 [106], turfgrasses can tolerate concentrations up to 1 mg.L-
1 [16, 105]. Under high boron content in irrigation water it is generally recommended to
remove the cuttings after mowing [16] as this is where boron is typically concentrated
and will help to ensure no build up occurs. Also care should be taken if other plant
species fall in the irrigation area or receive significant amounts of runoff. Soils may also
retain boron from the irrigation water leading to later toxicity issues. While soils will
adsorb boron to differing degrees evidence has suggested uptake is related more closely
to the water content than soil content [107] and this should be considered the more
important factor.
2.2.5.4 Metals
Metals in irrigation water can pose two significant threats: corrosion of irrigation
equipment and toxicity to the turf. The first of these relates only to some species, with
iron and manganese the two most important dissolved metals that can enhance
biocorrosion [108-111] and other metals such as copper enhancing specific corrosion
reactions. The studies performed during the development of the Australian and New
Zealand Guidelines for Marine and Freshwater Quality standards however suggest that
toxicity is the greater issue.
Table 2.21 shows the concentration limits recommended for irrigation waters by the
Marine and Freshwater Quality Guidelines. They define two limits based around the
length of expected use for the site. Where irrigation is anticipated for twenty years or
less the short-term trigger value (STV) can be used, otherwise the long-term trigger
value is more appropriate. The final column represents the contaminant loading limit or
the maximum allowable concentration of a certain metal in the soil. After twenty years it
is generally recommended that this concentration be analysed to ensure that the
irrigation water is not adversely impacting the soil.
The effect of metals in irrigation waters can vary dramatically, and while many are
necessary to plant growth, there is a very fine line between nutrition and toxicity. Some
of the metals may interact. A good example is the effect of copper and zinc. Both of
these metals act to prevent the uptake of iron so copper and zinc toxicity mimics iron
deficiency. High concentrations of these two metals appear to be the most significant
concerns in terms of alternate water sources [6]. Iron, on the other hand, is probably
less of a concern as some studies have shown that low level iron applications using
irrigation water is actually beneficial to turf growth [9].
42
Table 2.21 Recommended limits for metals concentrations in irrigation water. Long-term triggers
apply to 20 years use, while short-term apply to 5 years use. Adapted from [106].
Element
Suggested
Soil CCL
(kg/ha)
Long-term
Trigger
(ppm)
Short Term
Trigger
(ppm)
Aluminium (Al) - 5 20
Arsenic (As) 20 0.1 2
Beryllium (Be) - 0.1 0.5
Boron (B) - 0.5 *
Cadmium (Cd) 2 0.01 0.05
Chromium (Cr) - 0.1 1
Cobalt (Co) - 0.05 0.1
Copper (Cu) 140 0.2 5
Fluoride (F) - 1 2
Iron (Fe) - 0.2 10
Lead (Pb) 260 2 5
Lithium (Li) - 2.5 2.5
Manganese (Mn) - 0.2 10
Mercury (Hg) 2 0.002 0.002
Molybdenum (Mo) - 0.01 0.05
Nickel (Ni) 85 0.2 2
Selenium (Se) 10 0.02 0.05
Uranium (U) - 0.01 0.1
Vanadium (V) - 0.1 0.5
Zinc (Zn) 300 2 5
Metal contents in alternative water sources are going to vary dramatically. In general,
however understanding the catchment for the source will help in identifying what species
may be an issue. In general industrial sources are a high risk both in terms of
stormwater and recycled water. Stormwater catchments that include major roads such
as freeways or large commercial/light industrial estates would also be potentially
problematic. Rainwater or stormwater that is collected off metal roofs can also be an
issue. While all these sources can be treated to reduce the concentration of metals,
limiting catchments to residential sources with a small number of commercial sources
will help to ensure the lowest possible metal loadings and therefore safest water for the
turf.
2.2.5.5 Pesticides, Herbicides and Biocides
Pesticides and herbicides are obviously detrimental to turf growth even below parts per
million concentrations. There are a large number of these compounds and they are not
necessarily always present, but may come through in high concentration slugs. Testing
in general is very expensive and regular testing to identify if any are present is not
currently practical for large water projects let alone small decentralised systems. In
general it is best to know the catchment. Agricultural sources of water could be a
problem with pesticides as could some industrial sources. As with metals limiting the
catchment area to residential sources is probably the best technique in avoiding potential
problems with these compounds.
43
In general, biocides used in any alternative water scheme tend to be short-lived leaving
little residual and rely on short residence times to ensure high quality water reaches the
end use. The only biocide of concern is chlorine which can be added to recycled water at
very high concentrations. Highly oxidising chlorine is toxic to plantlife and care should be
taken to ensure the content in irrigation water is not too high. Scientific literature
recommends aiming to keep residual chlorine below 1 mg.L-1, although up to 5 mg.L-1
will result in only moderate effects [16]. The addition of sodium metabisulfite to water
can help remove chlorine, though at the expense of increasing salinity.
2.2.4.6 Carbonates
The bicarbonate and carbonate content of irrigation water is also critical in ensuring good
quality soil and turf. High concentrations of carbonates in the presence of calcium will
lead to precipitation and foliar deposits on the turf [5]. At very high concentrations these
carbonates can also increase the soils pH leading to decreased soil permeability and
bringing detrimental changes to microbial activity [16]. Literature recommendations
suggest bicarbonate should be maintained below 90 mg.L-1 and definitely not above 500
mg.L-1 [16].
2.2.4.7 Phosphates and Nitrogen
Phosphates and nitrogen source are vital to the growth turf. Introduction of these
important fertilizers to the grass as part of the irrigation water will ensure a constant,
low level application that is believed to be beneficial [16]. Total nitrogen in particular is
usefully applied in small doses over a long time period as this appears to improve the
health and colour of the turf [112]. The requirements do vary between species as shown
in Table 2.22.
The benefits of high nutrient content irrigation waters also apply to biological growth in
storage ponds and pipework, however. This could ultimately lead to biofouling of
irrigation pipework and the failure of the system. Excess nitrogen can also be
detrimental to the turf and actually result in the stunting of growth. The Marine and
Fresh Water Quality Guidelines suggest maintaining phosphorus levels below 0.05 mg.L-1
and nitrogen below 5 mg.L-1 for long term use (i.e. greater than 20 years of application)
[106]. Short term use will be heavily site specific, but concentrations of up to 125 mg.L-1
for nitrogen and 12 mg.L-1 for phosphorus may be achievable. The Australian recycled
water guidelines are slightly relaxed and suggest that no effects of nitrogen can be seen
at irrigation water concentrations below 30 mg.L-1 [5]. In terms of phosphorus they also
suggest maintaining contents below 0.05 mg.L-1 or monitoring of the system after 40
years at concentration around 0.2 mg.L-1. Higher concentration may be possible but
would require more regular monitoring of the irrigation system to ensure no blockage
has occurred.
44
Table 2.22 Nitrogen requirements for different turfgrass species. The requirements are given in
grams per square metre per growing month. The data was adapted from [9].
Species Common Name N requirements
(g.m-2
.month-1
)
Agrostis canina Velvet bentgrass 2.4 - 4.9
Agrostis capillaris Colonial bentgrass 2.4 - 4.9
Anoxopus Carpetgrass 1.0 - 2.0
Buchloe dactyloides Buffalograss 0.5 - 2.0
Cynadon dactylon Bermudagrass, couch 3.9 - 8.8
Eremochloa ophiuroides Centipedegrass 0.5 - 1.5
Festuca Arundinacea Tall fescue 2.0 - 4.9
Festuca Rubra Red fescue 1.0 2.4
Lolium multiflorum Italian ryegrass 2.0 - 4.9
Lolium perenne Perennial ryegrass 2.0 - 4.9
Paspalum Notatum Bahiagrass 0.5 - 2.0
Poa annua Annual bluegrass 2.4 - 4.9
Poa pratensis Kentucky bluegrass 2.0 - 3.4
Poa trivialis Rough bluegrass 2.4 - 4.9
Stenotaphrum secundatum St Augustinegrass 2.4 - 4.9
Zoysia Japanese lawngrass 2.4 - 4.9
2.2.5.8 Oil and Grease
Some water sources will contain oil and grease compounds that if left untreated are
detrimental to irrigation. Oil and grease compounds are a range of chemicals that are
soluble in non-polar (or organic) solvents. When applied to a soil rarely they are
degraded by microbial communities in the soil [113]. However, when applied regularly as
part of irrigation water a build-up of compounds will occur [113]. The hydrophobic
nature of the chemicals increases the soil’s water repellence and ultimately reduces the
effectiveness of irrigation [113]. They may also introduce water poor sections to the soil
as the oils cannot be flushed out by rainfall or irrigation [113].
45
2.2.6 Human Health
2.2.6.1 Introduction
One of the primary concerns expressed about the use of non-potable water is the
potential effect on human health. This comes from the perceived health risks associated
with different types of non-potable water, particularly pathogens and endocrine
disruptors in recycled water. The following is a discussion of the actual health risks
associated with non-potable water use for irrigation purposes and ways to reduce these
risks. There are generally two main categories of health risks: chemical of concern and
pathogens. Though both are considered in the following discussion, pathogens ultimately
represent the greatest risk. This risk is essentially eliminated where the Australian and
Victorian guidelines are followed in the establishment and the operation of a project.
2.2.6.2 Chemicals of Concern
Chemicals of concern refers to trace elements present in recycled water either from
industrial waste products or from health related excretions. Other chemicals may also
enter storm and rainwater after settling on the ground or rooftops and being collected by
the rainfall.
Recycled Water
There are a number of classes of compounds in the chemicals of concern category,
including mutagens and carcinogens. However the two groups generally discussed in
recycled water are endocrine disrupting compounds (EDCs), compounds that have an
effect on the hormonal balance of an organism, and pharmaceutically active compounds
(PhACs), compounds derived from pharmaceuticals that take part in the body chemistry
of an organism. One of the main problems with chemicals of concern is the large number
of potentially harmful compounds or compounds that are currently unknown that may
have an impact.
It is generally accepted that wastewater treatment processes remove amounts of these
compounds [114]. Research in Australian recycled water plants has suggested that
undetectable amounts in water after tertiary treatment are further reduced by
microfiltration and reverse osmosis (dual membrane filtration) processes [115]. This is
evidenced by detectable quantities in the RO brine. The trace level of most compounds
of concern in recycled water in general suggests there is little risk to their presence in
non-potable applications [116]. The unknown nature of the compounds do, however,
raise some cause for concern [117] although this is a point of contention.
Stormwater and Rainwater
Stormwater and rainwater have the potential to collect chemicals from the catchment
that may have accumulated on surfaces or result from the degradation of surfaces. In
the past recommendations have been made not to collect the “first flush” of rainwater or
stormwater because it was believed to be the most contaminated. Recent research
however suggests this is not the case [118] and the Australian guidelines do not
recommend this to try to control chemical contamination [6].
In rainwater use water quality would generally be high, but can be reduced by the
presence of certain characteristics of a roof. The Australian guidelines for stormwater use
46
strongly recommend using rainwater, or roof water, only where the following are not
present [6]:
• Copper or zinc roofing materials
• Public access (with the exception of maintenance access)
• Vehicular access
• Structures above a roof that may rust or corrode or provide a resting place for
birds
• Discharge, overflow or bleed-off/blow-down pipes from roof mounted appliances
such as air-conditioning units, hot water services and solar heaters
• A flue from a slow combustion heater that does not meet the relevant Australian
standard.
• A chimney or flue from any other process
• Exposure to chemical sprays from within the building (for example spray paint)
• Significant atmospheric deposition of pollutants (for example, from neighbouring
industrial facilities)
Other issues may include lead and bitumen based materials, asbestos or preservative
treated wood. While a project need not be precluded where any of these are present,
treatment may be required to prevent human and environmental contamination,
although the Australian guidelines feel the risk is suitably low that the exposure controls
required to manage biological risks would be sufficient to protect against chemical risks
[6].
Stormwater quality is also highly dependent on what may be in the catchment area.
Where a catchment is primarily residential and commercial the risk is considered to be
low and effectively controlled by the actions taken to manage biological risks [6].
However some issues that must be considered are outlined below:
• Industrial facilities – can generate high levels of metal and hydrocarbons
• Major roads, i.e. tollroads and freeways – can generate high levels of metals and
hydrocarbons
• Agricultural land – can generate high levels of pathogen and nutrient runoff
• Catchments with a high quantity of metal roofs – can generate high metal
loadings
• Streambank erosion and construction activity – can generate high levels of
suspended solids and turbidity.
In each of the above cases an in-depth study must be undertaken of the catchment and
considered in some detail. Extra treatment of the water may be required. Users should
refer to the Australian guidelines in such situations.
General
For all chemicals of concern to have an effect, large quantities have to be consumed on a
regular basis [114]. This would require someone to ingest copious amounts of water
over a long time period. In public space and sportsground irrigation such a situation is
not likely to occur. The main concerns would be with accidental consumption and cross
connection with potable water systems. These issues are discussed in Section 2.2.6.4.
47
2.2.6.3 Pathogens
Pathogens are biological agents that cause illness in their host. Table 2.23 lists the more
common examples of pathogens present in alternative water source. These fall largely
into four classes: bacteria, viruses, protozoa and helminths [119]. In raw sewage these
tend to be enteric pathogens (meaning they are common in the intestines of humans
and therefore in human sewage), however recycled water and other water sources may
also contain opportunistic pathogens (meaning they take advantage of favourable
breeding conditions and can be found in almost any location where conditions are right).
In general, although enteric pathogens are threats to human health, their nature means
that their source is well-known and they can be easier to control. Opportunistic
pathogens on the other hand can enter a system after disinfection techniques, via soil or
air, and present a greater, unknown threat.
Table 2.23. Common pathogenic species in alternate water sources.
Pathogen Type Species
Bacteria
Legionella spp.
Klebsiella spp.
Salmonella
Campylobacter
Pathogenic Escherichia coli
Shigella spp.
Yersinia spp.
Vibrio chloerae
Atypical Mycobacteria
Staphylococcus aureus
Pseudomonas aeruginosa
Viruses
Enterovirus
Adenovirus
Rotavirus
Norovirus
Hepatitis A
Calicivirus
Astrovirus
Coronavirus
Protozoa
Cryptosporidium
Giardia
Naegleria fowleri
Entamoeba histolytica
Helminths
Taenia (tapeworm)
Taenia saginata (beef measles)
Ascaris (round worm)
Trichuris (whipworm)
48
To determine pathogen concentrations and effects, indicator organisms and reference
pathogens are used respectively. Comparison of indicator organisms and reference
pathogens before and after treatment serves to act as a guide to reduction effectiveness
(most commonly defined as a log reduction that is to say how many orders of magnitude
the concentration has decreased) across the entire class. Reference pathogens on the
other hand have been established by the Australian Guidelines for Water Recycling [5] to
assess the consequences of exposure and assist in determining the appropriate level of
reduction required by the treatment process.
The four classes of pathogens and their indicator and reference organisms are discussed
below:
Bacteria
Bacteria are the most common pathogens. They are unicellular organisms that can breed
independently of a host. Bacteria typically have multiple host types, meaning they are
not exclusive to humans and can be spread through other animals. Typically quite large
populations are required for infection to occur. They are largely enteric and their
populations can be reduced effectively using disinfection as part of a wastewater
treatment program. They can never be fully eliminated however, and in storm and
recycled water systems some biocide (typically in the form of chlorine) must be used to
ensure the population does not re-establish [114]. Some opportunistic pathogens are
also a concern, particular those picked up in dust and dirt. There are growing concerns
about Legionella becoming a greater threat in water storage facilities as dust becomes
more common in the dry, warm conditions around Melbourne.
Table 2.23 shows the typical log reductions in pathogenic species from various
treatments. From this it can be seen that bacterial removal is effective with membrane
filtration, reverse osmosis and biocidal techniques such as chlorination, ozonation and
UV disinfection. These will focus on enteric bacteria reduction and will most likely be in
place at the treatment plant providing the recycled water. However, as previously noted,
bacteria do not need a host to multiply and opportunistic bacteria may enter the water
through other sources. This means that some onsite precautions may be required to
ensure regrowth does not occur. For details on this please see Section 2.2.6.5.
The presence of bacteria in water is typically measured using faecal coliform counts or E.
coli. The reduction of these common enteric bacteria is believed to be an effective
measure of the reduction of bacteria in general. The reference pathogen for bacteria,
according to the Australian Guidelines is Campylobacter [5]. This is due to its being the
most common cause of bacterial gastroenteritis in Australia.
49
Table 2.23 Indicative log reductions for various treatment processes. Adapted from [5]
Treatment
Indicative log reductions
E. coli Bacterial
pathogens Viruses Giardia Cryptosporidium
Clostridium
perfringens Helminths
Primary Treatment 0 – 0.5 0 – 0.5 0 – 0.1 0.5 – 1.0 0 – 0.5 0 – 0.5 0 – 2.0
Secondary Treatment 1.0 - 3.0 1.0 – 3.0 0.5 – 2.0 0.5 – 1.5 0.5 – 1.0 0.5 – 1.0 0 – 2.0
Dual media filtration (w/ coagulation)
0 – 1.0 0 – 1.0 0.5 – 3.0 1.0 – 3.0 1.5 – 2.5 0 – 1.0 2.0 – 3.0
Membrane filtration 3.5 - >6.0
3.5 - >6.0 2.5 - > 6.0 > 6.0 > 6.0 > 6.0 > 6.0
Reverse Osmosis > 6.0 > 6.0 > 6.0 > 6.0 > 6.0 > 6.0 > 6.0
Lagoon Storage 1.0 – 5.0 1.0 – 5.0 1.0 – 4.0 3.0 – 4.0 1.0 – 3.5 - 1.5 - > 3.0
Chlorination 2.0 – 6.0 2.0 – 6.0 1.0 – 3.0 0.5 – 1.5 0 – 0.5 1.0 – 2.0 0 – 1.0
Ozonation 2.0 – 6.0 2. 0 – 6.0 3.0 – 6.0 - - 0 – 0.5 -
UV Irradiation 2.0 –
> 4.0 2.0 - > 4.0
>1.0 adenovirus,
> 3.0
enterovirus, Hepatitis A
> 3.0 > 3.0 - -
Wetlands (surface flow) 1.5 – 2.5 1.0 - 0.5 – 1.5 0.5 – 1.0 1.5 0 – 2.0
Wetlands (subsurface flow)
0.5 – 3.0 1.0 – 3.0 - 1.5 – 2.0 0.5 – 1.0 1.0 – 3.0 -
50
Viruses
Viruses are the smallest pathogens. They are highly contagious, only requiring a small
number to cause infection (10 viral particles are often enough [114]). They have a
narrow host range, meaning viruses commonly found in birds will not easily jump to
humans. They are also unable to replicate outside the host. This means that disinfection
processes can reduce a virus to levels below that required for an infectious dose and that
the population should not re-establish. Consequently, where an effective disinfection
programme is in place at the water source, viruses should not pose a significant risk.
This view is supported by the World Health Organisation’s assessment of pathogen risks
in recycled water [119]. Having said this, the more significant health effects from viral
infection and lower infectious doses leads to greater log reduction requirements by the
Australian guidelines [5]. This in general means that viral risks dictate the treatment and
disinfection required in recycled water.
Virus removal can be effective with options such a dual media filtration, reverse osmosis
and ozonation (Table 2.24). As was noted previously, as long as the tolerable risk is
achieved at the water source, no significant risk will exist at the end use because viruses
need a host to replicate.
While detecting the presence of specific viruses is possible, it is expensive. The more
common approach is to use faecal coliforms as an indicator of when viruses might be
present and take corrective action accordingly. This is because the test for faecal
coliforms is easier, cheaper and more reliable than virus analysis. The reference
pathogens as outlined by the Australian guidelines are rotavirus and adenovirus [5].
Protozoa
Biologically, protozoa are unicellular organisms, distinguished by the presence of a
nucleus and outer membrane. More importantly they can exist outside a host as dormant
cysts or oocysts that will activate in the host under the right conditions. The main host is
man, although some other animals may affected. Common species are Giardia lamblia
and Cryptosporidium parvum [114]. They are highly infectious requiring as few as 10
(oo)cysts for infection to occur. In terms of their inactivation however, they are the least
understood of the pathogens.
Due to their large size, filtration techniques are often best for reducing protozoa levels as
indicated by Table 2.24. UV irradiation has also been found effective in inactivating
(oo)cysts and is currently used for this purpose by Melbourne Water at Western
Treatment Plant. Chemical disinfection (chlorination and potentially ozonation) on the
other hand appear to be less effective than with other pathogens. As with other
pathogens the focus of removal is on the water source.
In the past faecal coliform counts were used to determine the efficacy of removal of
(oo)cysts, however research has shown that there is little correlation between coliform
kills and (oo)cysts kills [120]. Cyst counts are now more commonly performed, but
recent investigations have suggested that this may not be a reliable indicator as between
75 and 97% of cysts after treatment are incapable of activating [121, 122].
Consequently, (oo)cyst counting will lead to a high number of false positives. However,
the large rate of (oo)cyst deaths in treatment plants means that protozoa are not
consider a significant threat in recycled water [121].
51
As noted above (oo)cyst counts of Giardia and Cryptosporidium are typically used as an
indicator for protozoa. By the Australian guidelines the reference pathogen is the more
difficult to remove Cryptosporidium parvum [5].
Helminths
Helminths are parasites such as hook worm, round worm and whip worm that reside in
the stomach and intestines of a host. They generally have complex life cycles, requiring
intermediate hosts to activate. The three previously mentioned are of greatest concern
as they have no intermediate host [114]. They are classified as the greatest risk in using
recycled water by the World Health Organisation [119] although their occurrence and
removal through filtration and detention systems (see Table 2.24) limits their impact in
Australian alternative water sources.
Helminths are rarely tested on a regular basis in Australian recycled waters, typically
being removed by filtration or pond detention. In Victoria checks are generally
performed to ensure that the treatment techniques effectively remove helminths on start
up. They should not pose a significant threat in irrigation, however they are of concern in
agricultural use. Open spaces that may be used or occupied by farm animals are of
particular concern and greater care should be used when assessing these sites for
recycled water use. In terms of reference pathogen, the Australian guidelines state that
Cryptosporidium parvum is an adequate measure for helminths as well as protozoa [5].
State and National Guidelines
The Australian guidelines [5-7] focus primarily on the health effects of alternative water
use and any consideration of this issue should be focused around the most current
version of these. The guidelines ask for each user to perform a quantitative risk
assessment aimed at producing “fit for purpose” water. This targets a reduced potential
for pathogenic infection below a tolerable risk threshold (in this case 10-6 Disability
Adjusted Life Years). Overall, the guidelines are designed to allow for greater flexibility in
water treatment and use options. The various guidelines have set specific log reduction
targets for municipal irrigation as shown in Table 2.25. Although there is still some
potential for variation this is a good target range. In order to achieve the required log
reduction there are two paths, the first is treatment with the log reductions shown in
Table 2.24. The second is in exposure reduction controls. These are listed in Table 2.26.
It is important for public space and sportsground professionals to understand these
requirements as they are often used to achieve the desired health effects and shift the
responsibility from water providers to water users. Those responsible for irrigation must
ensure that any criteria outlined as part of the provision of recycled water are followed
appropriately.
52
Table 2.25 Log reduction requirements for alternative waters to be used for municipal irrigation. Adapted from [5, 6]
Water Source Activity
Log reductions
Cryptosporidium Rotavirus Campylobacter Nominal
Minimum
Black Water
Municipal irrigation 3.7 5.2 4.0 5.3
Municipal irrigation +
Dual reticulation 5.0 6.4 5.1 6.5
Storm Water Municipal Irrigation 2.2 2.4 2.0 2.5
Rain Water Municipal Irrigation - - -1.1 No treatment
required
Table 2.26 Log reduction equivalents from on-site controls. Adapted from [5]
Control Measure
Reduction in
exposure to
pathogens
Withholding period (1-4 hours) 1 log
Spray drift control (microsprinklers, anemometer systems, inward
throwing sprinklers) 1 log
Subsurface irrigation 5-6 logs
No public access during irrigation 2 logs
Buffer zones (25-30 m) 1 log
53
As an example of the implemention of these guidelines, consider a public open space to
be irrigated with recycled water. A the bacterial, viral, protozoan (B,V,P) log reductions
of 3.7, 5.2, 4.0 are required. Using secondary treatment coupled with chlorination the
log reduction achieved is 6, 3, 1. A further log reduction of three is therefore required at
the site of irrigation to ensure public safety. This can be achieved by ensuring no public
access during irrigation (log reduction of 2) and one of the following:
• Withholding period, preventing public access for four hours after irrigation (log
reduction of 1)
• A 25 to 30m buffer zone (people prevented from entering) around the irrigated
area (log reduction of 1)
• Control of spray drift by using inward throwing sprinklers (log reduction of 1)
Water treatment to a higher quality (for example that uses secondary treatment followed
by membrane filtration and reverse osmosis giving a B,V,P log reduction of >6, >6, >6)
may not require exposure reduction controls, while other water treated to a lesser
degree may need significantly more. Each recycled water project will be different and
must be assessed on an individual basis.
2.2.6.4 Cross Connection and Accidental Ingestion
Cross connection and accidental ingestion represent one of the most significant health
risks in non-potable water uses. Though ingestion is the primary method for infection by
enteric pathogens, the risk of infection is generally low. The continuous ingestion of non-
potable water will significantly increase the risk however. There have been a number of
well-publicised cross connection issues recently. What is important to note about them is
that they are generally the result of human error and require strict management controls
to be prevented.
Where a high quality of water is used very large volumes would be required for any
effects to be seen [114]. Lower quality water may present a risk where biological control
have not been put in place. People’s perceptions of the water may not reflect this
however. In most cross connection cases people report (generally retrospectively)
gastrointestinal illnesses. Though these claims may be justified, there is also a degree of
paranoia that results from the discovery that the water they have been drinking was not
what the drinker believed it to be and there is no way of confirming this retrospectively.
Consequently it is important to manage the risk of cross connection and accidental
ingestion on site effectively.
Ensuring a non-potable water system is free from cross connections can be performed
using a two-pronged approach: differentiation of the non-potable water system and the
potable water; and system tests to ensure the water is what it is. It is also worth
mentioning that there is a certification course for plumbers with regards to recycled
water run by the local water provider. The Plumbing Industry Commission in Victoria
also has guides to recycled water plumbing.
The most well known aspect of recycled water pipelines is the need for a colour
differentiation from potable. The purple pipelines are standard throughout the world and
a legal requirement in Australia [123]. Furthermore the marking of the recycled water
pipelines and taps (with removable handles) as non-potable water is a legal requirement
and can prevent accidental ingestion.
54
Some parts of the United States require that recycled water pipelines running in parallel
to potable water lines be offset diagonally (ie both vertically and horizontally). This is
believed to reduce the risk of accidental cross connection. In Victoria the only legal
requirement is a separation of recycled water pipelines from potable of 100 mm above
ground and 300 mm below [123]. Also there is a requirement that connections to
recycled water taps and meters have different sized threads in order to minimise the
possibility of cross connection. Another option that has been suggested is the use of
pipes of different sizes. Where the potable water system is not used for fire protection
and can be made smaller, this has the added benefit of ensuring water quality is
maintained. In general the long residence times of potable water in large pipelines
reduces the water quality. Reducing pipe size decreases the residence time and provide
better quality water.
Testing of recycled water systems can be typically performed in two ways. The first is a
standard in most residential reuse schemes in the US and involves the depressurizing of
the recycled water system once a year. A similar system can be used in an industrial
application where the recycled water system can be depressurized during major plant
shutdowns allowing for a thorough check of the system.
The alternative is more extreme but is under consideration in Cary, USA after their
recent cross connection problems. After a new property is connected to the recycled
water system Cary officials will now test water directly from the tap of key properties.
The main differentiating parameter in recycled water will vary with treatment conditions,
however conductivity and chlorine residual are two key factors that generally vary. A
similar simplified system may be achieved using conductivity or chlorine residual in
industrial situations, with check being performed after major plumbing operations or
plumbing where potable water systems were affected.
2.2.6.5 General Controls – Disinfection
The general control to protect human health in alternative water uses are guidelines
outlining allowable uses based on the assessment of pathogenic health risks and barriers
between existing pathogens and people. These barriers will take the form of treatments
and exposure reduction controls as outlined previously. One of the more common
controls used across all water types is disinfection. It is important to remember that the
disinfection occurring at the treatment stage significantly reduce the presence of
pathogen, but not completely eliminate them. Also, bacteria are able to regrow without a
host and, as such, can increase in population where the water has a large residence
time, i.e. is left standing for a long period of time. In the case of recycled water, water
providers typically dose the water with large amounts of chlorine to both reduce
pathogen populations and to maintain some residual amount to prevent regrowth.
However this is depleted over time. As a general guide recycle water should still be
suitable for use where a residual greater than 0.3 mg.L-1 is maintained. Other water
sources should be used as soon as treatment has occurred [124]. If this is not possible a
biocide program may be required by the user. Though this is unlikely to be the case it is
discussed briefly here.
In order for biocidal control to be effective, the dosage should be scientifically selected. A
successful program will [125]:
• Know the target organisms
55
• Select the right biocide and its concentration
• Perform a scientific determination of the dosing frequency
• Monitor the control program
• Monitor attachment of micro-organisms to surfaces
In general oxidising agents are the most effective biocides as they act indiscriminately
and organisms cannot build up a resistance to them [125]. They do, however, suffer
from significant interferences reacting with many oxidisable substances such as organics.
The main oxidising agents that would be considered in an irrigation project are:
• Chlorine. In swimming pools and water treatment this is typically added as
sodium hypochlorite. The issue of salinity however may make the more expensive
calcium hypochlorite a more appropriate choice. This disinfection is highly non-
selective and suffers major interferences from ammonia and other nitrogen
compounds that are beneficial to turf irrigation as nutrient sources. Its residual is
easy to measure, but disappears quickly encouraging regrowth [125].
Importantly chlorine is toxic to turf species and any residual must be maintained
below 5 mg.L-1 and preferably below 1 mg.L-1 [16]. This means low level of
continuous dosage are more appropriate than shock dosing when regrowth
becomes an issue.
• Chloramination. Chloramines, formed through the reaction of chlorine with
ammonia, are becoming more popular primarily due to their high selectivity when
compared to chlorine. This means they are less corrosive to the environment in
which they are used and have a longer lasting residual. However, as chloramines
is less oxidising than chlorine it is slightly less effective and bacteria have been
seen to develop a resistance [126].
• Ozone. The decomposition intermediates of ozone are particularly effective as a
biocide. Unfortunately, ozone is not stable in water and will not maintain a
residual to prevent regrowth. It also breaks down organics to short chained,
oxygen-rich species that promote bacterial growth [125].
• UV irradiation. This is most effective at a wavelength of 253.7 nm [125]. It lacks
residual limiting it to point of use disinfection. An important limiting factor is
turbidity. Turbidity above 1.5 NTU seriously reduces the effectiveness of
disinfection. Some storm events can result in very high turbidity levels and
pretreatment to remove solids may be required in some systems.
• Hydrogen Peroxide. While not effective on its own, it can be used in conjunction
with UV irradiation to generate highly oxidising species that are both bacteriacidal
and sporicidal [125].
Oxidising agents, though effective may also be problematic in their potential threat to
steel, wood [124] and turf species [16]. Large dosages should be avoided and
continuous, low levels applied instead. While other biocides are available they are
probably not applicable to irrigation due to their cost.
2.2.6.6 Employee Health Protection
There are a number of important steps that can be taken to ensure employee health and
safety when using non-potable water. It should be remembered that the water quality
from any other than a potable supply should be considered non-potable. Australian
guidelines for using recycled water, including stormwater, give treatments and control
that make a water fit for purpose only and not necessarily for drinking. The steps you
56
would take to protect employees may vary depending on the different water qualities,
sources and their use and are generally outlined in the Victorian and Australian
guidelines [5-7, 123] (please refer to these documents for the most up to date
protocols). These protocols should be communicated as part of an induction for all
people (direct employees and contractors) that are on site during irrigation or in direct
contact with the water used for irrigation.
• Employee and contractors should understand what uses of the water are
acceptable and what are not. They should also be aware of any controls required
for irrigation using the water.
• Food, drink and cigarettes should not be consumed where non-potable waters are
used.
• After using recycled water employees should wash their hands immediately
• All wounds should be covered with a waterproof dressing when working with non-
potable water.
• Any skin rashes of illnesses should be reported to a supervisor who will in turn
report to an OH&S specialist for investigation of the incident.
• Workers with dermatitis, chronic illnesses or weakened immune systems (either
due to illness or medication) should be assessed by a medical professional before
using or working in the vicinity of recycled water.
• Where raw sewage or Class D recycled water is used on site (i.e. where treatment
is provided onsite) immunization may need to be considered against particularly
harmful viruses such as hepatitis. This applies to worker who will be in contact
with the water or around the treatment plant.
• Where stormwater is used hepatitis A immunization is generally recommended.
• All non-potable water taps should be labelled as being such, and should have the
tap itself removed when not in use. There should be signs prominently displayed
around the site indicating that non-potable water is used onsite.
• All employees should be made aware of procedures or problems related to the
use of non-potable water. There should also be encouragement to report
incidents.
2.2.6.7 Animal and Livestock Health
This report has not been prepared to consider agricultural sites. There is always the
issue of domestic animals being present from organised groups such as obedience and
agility training as well as casual users of sports fields and open spaces. Some turfed
spaces are also occasionally used for fairs, circuses and agricultural shows. Consequently
the potential effects to animals should be briefly considered.
There are a number of animal-based pathogens that may be present in a number of
water sources particularly recycled water and stormwater. These are unlikely to be
present in quantities similar to human-specific pathogens, but there are some pathogens
that are also of concern to other animals, for example Giardia lamblia is also capable of
infecting domestic cats and dogs [127]. While the Australian guidelines in general don’t
consider animals, the risk assessment they propose has the ability to be expanded if a
dose-response value for the infection of the animal can be determined. It may be
appropriate to consider the health implications to animals, where these commonly use a
site, using the Australian guidelines as a template.
57
Of all the animals to consider the most important are pigs. The main risk is the helminth
Taenia solium, or pig measles. This tape worm uses pigs as an intermediate host. If an
infected pig is consumed by humans a particularly severe infection results that can lead
to serious neurological effects. As a consequence of this federal government regulations
forbids the use of recycled water where it may contact pigs or pig fodder [5].
2.2.7 Perceptions
2.2.7.1 Public Perception
When considering non-potable water for irrigation it is important to understand how
users will react. In a lot of cases the reaction will be negative. There is much discussion
in the media about the significant energy requirements of desalination. There is also
considerable discussion in the literature and media about the “yuck” factor associated
with most non-potable waters, while for rain and storm water this is not as severe. While
rain and stormwater are not immune to this effect, the strongest reaction is typically
reserved for recycled water. It is considered a psychological aversion that arises from
the belief that after contact with sewage the recycled water is tainted or contaminated.
Similar psychological aversion can occur for stormwater which must have had contact
with dirty and contaminated roads, footpaths and carparks not to mention industrial sites
and hospitals. A study into the psychological effects of drinking different type of non-
potable water and from eating foods grown with the same waters showed 20% of
respondents suffered a feeling of disgust despite the fact that the sample was actually
potable water [128]. Psychological effects will not be easy to overcome.
Investigations into public acceptance typically look at domestic uses and focus on
potentially adding a traditionally non-potable water to a drinking supply. These have
highlighted some important trends:
• Public acceptance is strongly tied to the intimacy of use [128]. That is to say the
closer the water comes to a person, the more likely they will be opposed to it.
Irrigation water has a fairly low intimacy of use and will suffer from less
opposition than drinking or dual piping around the home.
• Public acceptance will decrease when a use is salient [129]. This is the equivalent
of the NIMBY (not in my backyard) effect. While people may be in favour of using
non-potable water for irrigation in principle, when told it will be happening at
their local park or sports field opposition will increase.
• Public acceptance of recycled water is directly related to trust [130]. This is
probably the most important aspect of recycled water use. The public will be
more accepting of recycled water where they feel the proponents (the
government, water authorities or company producing the water and the end user)
can be trusted. This will also mean that the process by which a project advances
should be open and transparent so people can understand how the decision
process occurred.
• Public acceptance is related to knowledge [131]. This is an obvious relationship
and may be addressed through community education and outreach. However, the
success of these programs in overcoming the “yuck” factor may be limited, as
this feeling is psychological in nature and cannot be considered the result of a
“rational” decision. The Australian Guidelines for Recycled Water contains a
chapter devoted to the development of community outreach and education
programs [5].
58
As stated earlier public acceptance of water uses tend to focus on domestic applications
such as drinking or washing. Irrigation of public spaces, golf courses and sports fields
are typically considered to be generally acceptable to the public. This is reflected in
studies that suggest for recycle water that acceptability lies in the range of 82 to 97%
[129, 132]. There are different degrees of acceptability however. The terminology used
in the studies above often accounts the variability in results. High acceptability is seen
for golf courses and parks [132], while this decreases when described as schoolyards
and playing fields [129]. This could be related to perceived exposure and the protection
of family from exposure from perceived threats.
There will also be variation with different water sources. Dolnicar and Schafer [133] have
investigated the acceptability of using recycled water versus desalination seawater for a
number of applications. For municipal irrigation purposes it was shown that acceptability
was 10-11% higher for recycled water (82-83%) over desalinated seawater (71-72%).
This was largely associated with the energy requirement and environmental impacts of
desalination when compared to producing recycled water. In general recycled water was
deemed more appropriate for almost all external uses that did not involve direct contact.
Other comparative studies, looking at recycled water, grey water and storm water, have
focused on the intimate use of drinking water and therefore may not be valid for
evaluating irrigation acceptability. However, environmental concerns do not vary
significantly between these water sources and psychological effects are likely to rule. The
trends therefore may be considered valid. One of the more extensive studies was
performed by the CSIRO and looked at perceived health risks and feelings of disgust
associated with stormwater, grey water and recycled water [128]. In terms of drinking,
the perceived risks were seen in the order from best to worst stormwater (~58%
perceived health effects), grey water (67%) and recycled water (79%). Feeling of
disgust followed a similar trends with 5% disgusted by stormwater, 10% for grey water
and 22% disgusted by drinking recycled (sewage) water.
Though there are no clear studies into acceptability of different alternative water sources
for irrigation, an order from most acceptable to least, may be derived from the above
studies: stormwater as most acceptable followed by grey water, recycled water, and
finally desalinated seawater as the least acceptable.
2.2.7.2 Employee Perception
Maintaining a positive image to the use of non-potable water onsite is also a very
important issue. Negative images or publicity can halt a project in a similar way to
community objections. One very potent example of this is the BlueScope Steelworks in
Port Kembla [134-136]. In this instance the union of the New South Wales fire brigade
refused to fight fires at the site due to the use of recycled water in the plant’s fire control
system. Citing potential health effects a protracted industrial action was fought between
the union and the New South Wales government, during which time the plant was
provided with potable water, while recycled water was sent to ocean outfall. The union
was requesting indexed death and disability benefits for financial protection if they
became ill from using the water [137]. The issue was eventually solved by arbitration
from the Industrial Relations Commission.
In general, employee concerns are going to be with the safety of the water. Keeping
employees on side will require open and transparent communications from management
59
particularly focusing on this issue. It should be remembered there are two primary
health concerns in non-potable waters: trace compounds (e.g. endocrine disrupting
compounds, hydrocarbons and pharmaceuticals) and pathogens (e.g. bacteria, viruses
and protozoa). The use of non-potable water for irrigation limits exposure and ingestion
and therefore leaves only infection from pathogens as a risk. Where rainwater or Class A
recycled water is used, there is no significant risk as these waters are generally
considered pathogen free or very close to. Storm water and Class B and C recycled
waters will be disinfected, but should still be treated with caution and will require some
controls and barriers.
When using non-potable water, a thorough communication strategy between
management and the workforce should be enacted. This should encompass:
• Communicating exactly water the water is (both source and quality), where it will
be used and what health controls are in place
• Explain how using non-potable water may change irrigation practises
• Determine and address worker concerns
• Explain procedures on reporting issues and how issues will be resolved during
operation
Further ideas may be found in the Australian guidelines [5]. It is important that, at all
times, communication is two way and open. This will ensure employees will feel
confident that the changes made onsite will not affect them or their health.
2.2.7.3 Image
Although not strictly a business, local governments operate on a similar level and image
is important in attracting local investment and increasing population. Since the growth in
the environmental movement in the 1980s and 1990s environmental issues have
become entrenched on the public agenda. Use of alternative water sources to maintain
resources that are important to the public should help to improve the image of a local
government area. Efforts should be made to highlight the environmental commitment of
the council, stating specific local improvements, not just just generalised information.
Possible benefits to consider are:
• More potable water now available for drinking
• Sporting fields and parks are drought-proofed for long term community
enjoyment
• Decreased pollution loads at traditional discharge points such as sewage or
stormwater outlets that will improve the quality of local creeks or beaches
• Maintaining groundwater levels preventing seawater intrusion or simply to ensure
sustainable use of groundwater sources
• Reuse of a valuable public resource, reducing the ecological footprint.
Evidence suggests that businesses gain a competitive advantage from strong
environmental performance [138]. It is possible that green councils may also do well at
attracting these businesses and investment if their environmental image is equally high.
Another point to consider is recognition programs. These programs are useful to enter as
the proponents will need to investigate what is being done and how it may be improved.
Importantly these awards provide a free and positive marketing platform for the winners
and the runners up regardless of their focus. Some of the awards of interest include:
60
A. savewater! Awards
(http://www.savewater.com.au/)
Identifies products, organisations and individuals who have demonstrated innovation
and commitment to deliver efficient water usage.
B. Banksia Environmental Founation Award
(http://www.banksiafdn.com/)
The Banksia Foundation supports and recognises members of the community that
have made a significant contribution to the environment. There is a water category
that is awarded to an organisation that has enhanced or conserved freshwater and
marine environments. There are also categories for climate (reducing greenhouse gas
emissions) and sustainability (minimising the ecological footprint).
C. Premiers Sustainability Awards
(http://sustainabilityawards.vic.gov.au)
These awards recognise individuals and organisations that have made a substantial
effort towards reducing their environmental impact.
D. Grow Me the Money
(http://www.growmethemoney.com.au)
This is a rewards program rather than awards. By joining the project and performing
environmental initiatives, organisations can earn points. These points can be
redeemed to obtain support from consultants, training and education and access to
resource efficient products. The recognition program has four levels that can be used
by members for 12 months. Increasing through the levels requires commitment to
the program. The program will also help by providing intense media coverage of the
efforts made by the members.
61
CHAPTER 3 – Water Sources
3.1 Introduction
An understanding of potential water sources is important to any irrigation manager. In
times of water shortage this is especially so. In the previous chapter general water
quality concerns were considered. In this chapter the individual water sources will be
considered and most likely contaminants investigated. As such there will be some
samples of water qualities for each water type. When looking at these qualities it is
important to remember that water sources can vary considerably. Wherever possible this
is highlighted. It is also important to keep in mind the quality of potable water as a
comparison. This is shown in Table 3.1.
The following sections are structured in roughly the same way looking at general
definitions of the water category, important quality issues, treatment techniques and
advantages and disadvantage. Each of these is generally tailored to irrigation of sports
fields.
3.2 Rain Water/Roofwater
3.2.1 Introduction
Rain water, or roof water, is used to refer to water that falls only on the roofs of houses
or buildings. It is considered separately from stormwater as it is generally collected at
the site of use and has not contacted surfaces that are generally perceived as polluted,
such as roads and gardens. Rain water can be a common source of drinking water is
some parts of Australia and is quite heavily used in irrigation of gardens in an urban
environment. The National Guidelines for Water Recycling considers rain water as a
source of irrigation water within Phase 2 [6]. The current understanding of rain water
and issues associated with its use in irrigation are discussed below.
62
Table 3.1 Representative potable water qualities in the Greater Melbourne region.
Parameter Units
City West Water [139] Yarra Valley Water [140] South East Water [141] Barwon Water [142]
General Altona Footscray Tullamarine Broadmeadows General Dandenong Lovely Banks Highton
Min Max Mean Mean Mean Range Range Min Max Mean Mean Range Range
Free Chlorine mg.L-1
0 0.85 0.1 0.05 0.06 0.01-0.45 0.02-0.28 0.09
Alkalinity mg.L-1
as CaCO3 10 13 12 11 11 12 18 15
Aluminium mg.L-1
< 0.01 0.08 0.02 0.02 0.02 0.02 0.09 0.05 < 0.01 - 0.047 < 0.01 - 0.031
Ammonia mg.L-1
0.003 0.01 0.006
Calcium mg.L-1
7.1 8.9 7.4 7.6 7.6 2.9 7.1 4.9
Chloride mg.L-1
13 16 15.4 16 16 6 8 7
Colour Pt/Co (CWW,
BW), HU (SEW) < 2 7 2 2 2 5.9 < 1 - 20 < 1 - 19
Conductivity uS.cm-1
55 140 107 114 113 7 72 54
Copper mg.L-1
< 0.004 0.032 0.008 < 0.004 0.015 0.004-0.140 0.011 - 0.150 0.002 0.66 0.04 0.003 - 0.17 0.004 - 0.07
Fluoride mg.L-1
0.7 1.08 0.9 0.9 0.9 0.61 1 0.88 0.07 - 0.1 0.07 - 0.09
Hardness mg.L-1
as CaCO3 23 29 26 27 27 11 - 18 11 - 16 12 20 16 30 - 100 30 -37
Iron mg.L-1
< 0.02 0.24 0.02 0.02 0.02 0.03 - 0.17 0.03 - 0.12 0.06
Magnesium mg.L-1
1.6 2 1.8 1.9 1.9 0.9 1.4 1.2
Manganese mg.L-1
< 0.01 0.03 < 0.01 < 0.01 < 0.01 0.001 0.034 0.007 < 0.002 - 0.014 < 0.002 - 0.036
Nitrate mg.L-1
0.84 1.37 1.18 1.2 1.24 0.041 0.2 0.11
pH units 7 9.7 7.5 7.6 7.4 7.0 - 7.4 7.0 - 7.5 7.3 7.4 - 8.7 7.1 - 8.3
Potassium mg.L-1
1 1.2 1.1 1.1 1.1 0.6 0.8 0.7
Silica mg.L-1
5.2 6 5.6 5.7 5.6 5.5 7.7 6.6
Sodium mg.L-1
6.7 9.3 8.2 8.9 8.3 3.9 5.6 4.7
Sulphate mg.L-1
7 12 10.5 11 12 1 2 2
TOC mg.L-1
1.3 1.9 1.5 1.5 1.4 1 2 1.5
Total Phosphorus mg.L-1
< 0.003 <0.003 0.003 < 0.003 < 0.003 0.006 0.09 0.016
TDS mg.L-1
57 70 67 69 68 24 70 47
Turbidity NTU 0.1 9.6 0.6 0.4 0.5 0.50-1.20 0.40-1.40 0.6 < 0.1 - 4.6 < 0.1 - 1.1
63
3.2.2 Quality issues
3.2.2.1 Chemistry
Rainwater quality is generally very good with only low levels of the main constituents of
concern. Typical qualities of water capture from a roof catchment are shown in Table
3.2. The good quality of the water can however, makes variations more pronounced.
Studies have shown that different types of storms will result in different water qualities
[143]. Ultimately this comes down to the location where the storm formed and areas
where the storm passes. For example storms that form over the ocean will have higher
salt contents in their water and are little influenced by atmospheric pollution [143]. On
the other hand those that pass over desert regions will contain some minerals including
magnesium, potassium and silicates [144, 145]. The presence of lightning in
thunderstorms can also change the composition of rainwater, with pollutants more easily
oxidised by the presence of ozone in the storm clouds ultimately leading to a more acidic
rain [143]. While collected materials during storm formation and movement will account
for some ionic loading, another significant source is “wash out”, that is the collection of
atmospheric pollutants while the rain is falling. This can result in acidity in rainwater (like
the acid rain phenomena) [143], increased salinity from sea spray [146], and metals
from fossil-fuel burning [97]. Prediction of rainwater quality based on location is difficult
but should consider the following:
• Distance to salt water/ocean: Sodium and chloride concentration in rainwater
are generally due entirely to dissolved sea spray [144]. The distance from a salt
water source appears to correlate to the contents of these two ions [97, 146].
Predominant wind direction is also a contributing factor with sea-based winds
contributing greater salt loading than land-based [97]. The concentration of
chloride ions in rainwater have been reported in the range of 0.4 and 3000 mg.L-1
in the past [146]. If the sodium content matches or is similar to this it cannot
always be assumed that collected rainwater is suitable for irrigation. It should be
noted however, that the upper concentration reported above is extreme.
Concentrations of strontium, magnesium, rubidium and potassium may also be
elevated as a result of sea spray.
• Location near major industrial emission sites: Heavy industrial sites and
heavy large vehicles use can result in elevated metals contents. Previous studies
in Newcastle, New South Wales have shown increases in As, Cd, Cr, Co, Cu, Fe,
P, Pb, Mn, Se and Zn content in rainwater associated with heavy diesel traffic
nearby [146]. In general these were not believed to have increased beyond legal
limits. Acidity or pH on the other hand does not correlate well with fossil fuel
burning. Studies in both Newcastle [97] and the Latrobe Valley in Victoria [147]
have been unable to see any trend with pH as a function with distance from
industrial sources of NOx and SOx gases, in contrast to studies in the Northern
hemisphere [143]. It has also been suggested that local cement works can
contribute elevated levels of calcium, silica and sulphur to rainwater, although
this has not been conclusively proven [148].
• Time since previous storm event: Though not obviously related to location,
the collection of pollutants and dust in the atmosphere and on the surface of the
roof can result in increased contamination once a storm arrives. If a rainwater
collection system is established in an area with high occurrence of short storm
events followed by long dry spells this should be taken into account.
64
Table 3.2 General roof water tank water qualities
Component Global Average
[149]
Newcastle,
Tank
[150]
Newcastle,
Tank,
Coastal1
[97]
Newcastle,
Tank,
Inland1
[97]
Ammonia (mg.L-1
)
0.2
Barium (mg.L-1
)
0.009634 0.005
Cadmium (mg.L-1
) 0.00066 < 0.002 0.00023 0.00009
Calcium (mg.L-1
)
1.19
Chloride (mg.L-1
)
6.65
Chromium (mg.L-1
)
0.00014 0.00004
Copper (mg.L-1
) 0.061
0.342 0.00088
HPC (cfu.mL-1
)
10
Iron (mg.L-1
)
0.06 0.428 0.00333
Lead (mg.L-1
) 0.054 < 0.01 0.0127 0.00582
Magnesium (mg.L-1
)
2.11 0.43
Manganese (mg.L-1
)
0.0706 0.0112
Nitrate (mg.L-1
)
0.05
Nitrite (mg.L-1
)
1.3
pH 5.7 6
Potassium (mg.L-1
)
4.24 0.343
Pseudomonas spp.
(cfu.100mL-1
) 110
Sodium (mg.L-1
)
4.03 13.2 3.53
Strontium (mg.L-1
)
0.0209 0.00257
Sulphate (mg.L-1
)
2.16
TDS (mg.L-1
)
105
TP (mg.L-1
) 0.15
0.0933 0.0407
TSS (mg.L-1
) 47 97.55
Turbidity (NTU) 9.1
Zinc (mg.L-1
)
10.2
(Zn-based roof)
0.34
(Non-Zn roof)
0.875 0.166
1. These two samples were summertime sample and were significantly different from winter samples.
Once rain hits a roof, additional sources of contamination must be considered. One point
of local variation is materials that deposit on the roof. Sea salt may contribute more salt
to the water at this point as can local soil/dust materials. Importantly local industrial
activities may impact on the site from dust or aerosol emissions. There is a common held
belief that discarding the “first flush” or rainwater will minimise this, however this
principle does not hold for all potential contaminants [118] and the national guidelines
do not recommend this [6]. Despite this short rain events have been shown to result in
spikes in the conductivity of water collected in rain tanks that are not seen in sustained
rain events [97]. Some wash off of contaminants should be assumed to occur, however
with the generally high quality of water collected, this may not be a concern.
65
The construction material on the roof, tank and piping is one of the more important
things to consider when collecting rainwater for irrigation use. A number of studies have
shown elevated levels of a number of metals, often exceeding drinking water guidelines
[97, 151]. This comes about due primarily to corrosion and leaching. Galvanised steels
and irons as roofing and tank materials are of particular concern showing elevated levels
of zinc [96] that can be a potential threat to turf. Copper piping and fittings are also a
concern with studies showing concentrations of copper 380 times greater than sites
without these [97]. These two in particular are of concern, according to the Australian
Guidelines, when irrigation is the end use [6], although other studies have shown
elevated levels of lead, iron, cadmium, manganese, aluminium [96] and nickel [97].
Levels potentially in breach of guidelines have been reported for cadmium, iron and zinc
in one Australian study [151] and lead and iron in another [97]. In the second case this
occurred during summer when elevated temperatures may also accelerate corrosion
processes. Importantly, studies investigating compliance with the national recycled water
guidelines have shown aluminium, iron, lead and zinc levels were exceeded on some
occasions [152]. Zinc concentrations in particular were elevated with levels as high as
11.5 mg.L-1 recorded at one site. The Australian Guidelines for Water Recycling generally
recommends against direct use of rainwater harvested from galvanised roofs in irrigation
and suggest limiting irrigation to 300 mm.yr-1 where this cannot be avoided [6].
Maintenance practices on roof catchments are also important. Build-up of leaf matter on
rooves can lead to increased corrosion rates and biological growth due to the stagnation
and ponding of water. Importantly, it is also possible to leach tannins and other
compounds from the leaves that will lead to a discolouration of the water [97] and
potential increase in toxic components. This may not lead to an issue with turf quality,
but can impact user’s perceptions of the water. The Australian Guidelines for Water
Recycling recommend using roof spaces with no overhanging branches. Where this is
unavoidable, regular (2 weeks to monthly) inspection and cleaning of roofs that are
being used to collect rainwater are vital to the efficient running of the system.
Water quality is also dependent on the tank’s residence time, or the amount of time the
water takes to pass through the tank. Studies have shown that rainwater pH is
dependent on the amount of time it is stored for with the pH dropping over time [97].
Using water quickly should allow water to maintain a pH of 5-6.
3.2.2.2 Biology
The biological risks of rainwater use come primarily from the ecology of the storage
tank. Here, long residence times and near-stagnant water can provide an environment
that encourages the growth of micro-organisms. The roof, on the other hand is generally
a hostile environment to micro-organisms. High temperatures and significant UV
irradiation should impact on microbial populations [153]. Unless ponding or pooling of
water occurs, bacteria should only be able to wash into a rainwater tank if they have
reached the roof during or just prior to rain. In general there are two pathways bacteria
may enter a rainwater tank: animal sources and airborne/dustborne bacteria [94].
Until recently, animal sources, particular faecal matter, were believed to be the primary
source of microbial contamination of rainwater. Birds and possums are typically
nominated as a source of enteric bacteria that are potentially harmful to humans. The
Australian Guidelines for Recycled Water focus on pathways to reduce this risk such as
ensuring there are minimal branches and other objects overhanging a roof [5]. This has
66
the added benefit of reducing the possibility of a build-up of leaves on the roof space.
Where these guidelines are followed there is generally minimal problems from
contamination by enteric bacteria and log reduction requirements are minimal for
irrigation as an end use.
Of potentially greater significance is the entry of other bacteria that are not enteric.
Studies of Australian rainwater tanks from the east coast have shown significant
bacterial contamination [94]. These non-enteric bacteria significantly outnumber their
enteric counterparts, suggesting that coliform or E. coli counts may not be sufficient for
determining potential health impacts from water [94]. Their spread appears to be
dependent primarily of local wind strength and direction, with stronger winds resulting in
higher bacterial counts [153]. The species that are most prevalent include Acidovorax,
Hydrogenaphaga, Polaromonas, Variovorax and Pseudomonas spp. [94]. Not all these
bacteria are necessarily dangerous to human health, but some, such as Pseudomonas,
can exacerbate skin conditions. Some other pathogens, such as Klebsiella and
Legionella, are also of concern due to their ease of spread and ability to cause infection
from aerosols. It should be noted however that only Klebsiella has been identified in
rainwater tank in Australia to date and this was in significant numbers [94]. To minimise
human health impacts from rainwater some disinfection should be performed.
Another important consideration is the theory that the ecosystem that establishes in
rainwater tanks is actually beneficial to water quality. It seems likely that the bacteria
commonly found in rainwater tanks are better adapted to these conditions and can out
compete enteric bacteria keeping their numbers low [94]. It has also been shown that
water quality improves as it passes through the tank [150]. These two observations are
of importance as it implies that disinfection of water in the tank could actually be
detrimental to water quality and suggests that disinfection should occur outside the tank
as water is removed using techniques such as ozonation or UV irradiation [94].
3.2.3 Treatment
In general rainwater should not require ant treatment before use in irrigation. This view
has been supported in the Australian Guidelines for Water Recycling [6]. With this in
mind, some researchers believe that the microbes that survive in a water tank may need
to be eliminated before use [94]. Where this is the case, the effectiveness of these
microbes in improving water quality and reducing the numbers of enteric bacteria
suggests that full tank disinfection is not advisable [94]. Instead in-line disinfection just
prior to use utilizing either ozonation or UV disinfection may be the preferred option.
3.2.4 Inherent Benefits
Rainwater is the most pure recycled water meaning it is suitable for irrigation without
significant treatment. This means there is minimal capital outlay, very small space
requirements and very few ongoing costs. In terms of energy requirements rainwater
relies on energy only for pumping and potentially for disinfection. These requirements
will be common across all alternative waters and suggest that the carbon footprint
should be least for rainwater.
The other significant benefit of rainwater is the legal issue of water rights. It is generally
assumed that rain falling on a roof within a property boundary can be used by the
property owner. Agreements with other property owners can complicate this issue
67
somewhat, however it is clearer than other water sources such as stormwater and sewer
mining.
3.2.5 Potential Disadvantages
While rainwater is a sustainable water source it is still climate sensitive. Periods of
drought and low rainfall, the time period when a turf will require significant irrigation,
will mean little water is available from this source. The size of the catchment (i.e. the
amount of roof space available) and the size of the storage tank dictate the amount of
water that will be made available. With this in mind it is unlikely that roofwater could
serve as the only source of irrigation water for a water hungry turf and another source
would be required to complement it and help make up any shortfall.
3.2.6 Conclusions
Rain water as a relatively clean water source should be usable without treatment for
irrigation. While care should be taken to reduce the impact of dissolution of galvanised
metals, copper and lead, the water can still be used for irrigation with careful
monitoring. While it will suffer in terms of water availability during times of drought, it is
generally an inexpensive and simple way of meeting at least some of the irrigation
requirement of a sports field.
3.3 Stormwater
3.3.1 Introduction
Stormwater is the rain water collected, generally across a large area, from practically all
surfaces within a catchment. This means the water has come into contact with sources
typically seen as contaminated such as roads, footpaths, gardens and open space. It
generally is slightly lower in quality than roof water, however it is also available in larger
volumes.
Unlike roofwater, stormwater does not become immediately available once rain starts to
fall. Surfaces can act as filters to slow down the flow of water, particularly where the
surface is pervious. Also, it cannot be assumed that all water that falls in a catchment
will be available. While the water from roofs, roads and pavements that are directed
towards collection systems will generally become available quickly, runoff from surfaces
such as gardens, open space and bushland will be partially retained and retarded by the
surfaces reach a collections point significantly slower, with flows sometimes arriving days
after a significant rainfall event. This makes modelling and designing treatment systems
and irrigation systems that rely upon them more difficult.
3.3.2 Quality Issues
Though it is sourced primarily from rain water, stormwater is typically of a poorer quality
due to the pollutants that are collected in wash out from surfaces. Unlike roofwater,
stormwater is affected more by the catchment than storm-based impacts. In determining
the suitability of stormwater or treatment that may be required, the characterization of
the catchment must be considered.
68
A detailed discussion on rain water harvested from roofs is provided in Section 3.2.
Briefly, the main concerns are the material the roof and collection system (down-pipes
etc.) are made from. Copper-based products and galvanised irons and steels will
contribute significantly to zinc and copper concentrations [96, 97], while lead from lead
flashing on tile roofs can also be significant [152]. Importantly, there is definitely less
(more likely no) control over the maintenance of roofs that could lead to increased
bacterial loads. There would also be no control of roofs that may have exhausts (such as
chimneys or heating exhausts, air conditioning units, exhausts from industrial or
laboratory process). These may contribute greater loadings of some toxic chemicals,
specifically metals and organic compounds, as well as opportunistic bacteria such as
legionella where evaporative air conditioners are not well maintained. Disinfection should
always be employed in storm water treatment.
The walls of houses will also contribute to the chemical loading of stormwater. The main
points of interest are zinc from painted walls, copper from bricks [154] and wood
preservative from various sources [155]. In general, both of these contaminants are
associated with wooden or weatherboard walls and are only of interest where there are a
large number of dwellings made from these materials in a catchment.
Pavements including footpaths and courtyards will contribute mainly to the calcium
loading of stormwater [156]. Alkalinity (CO32- concentrations) also increases on concrete
pavements [118]. Calcium, either from erosion or dissolution of concrete and cement,
will typically be present in higher concentrations than sodium salts. Typical
concentrations for important species are shown in Table 3.3.
The contribution from roads will vary significantly depending on the level of traffic [157],
the composition of the traffic [97] and the material of the road. Concrete surfaces will
contribute more calcium and alkalinity as noted previously [118, 156]. Residuals from
diesel combustion including arsenic, beryllium, cadmium, chromium, cobalt, lead,
manganese, silicon and selenium will be more common where heavy vehicles are
common [97] while zinc and copper from tyres and brakes respectively [154] are
believed to be related to traffic densities. Polyaromatic hydrocarbons are also related to
traffic densities as a residual of fuel combustion. Interesting, the levels of phosphorus
and nitrogen correlate to decreasing traffic density [149]. This is believed to be due to
vegetation encroaching on roads with low traffic volumes and contributing to the runoff.
Where deicing is employed these salts (typically sodium or calcium based) will contribute
significant quantities to stormwater. Examples of road runoff qualities are shown in Table
3.3.
From residential catchments the other major contributor are gardens and open space.
Typically these will result in higher concentrations of phosphates and nitrogen
compounds due to the heavy use of fertilizers [149]. This increased level of nutrients
typically is reason for stormwater treatment prior to it being discharged to a
watercourse. Gardens and open space may also contribute to higher salt loadings from
these compounds. Pesticides and herbicides will also be present in runoff from these
areas. If the contribution from these surfaces is high then it will be particularly
detrimental to irrigation and treatment to remove these compounds will be necessary.
69
Table 3.3 Typical stormwater runoff qualities from different surfaces.
Parameter Roads
[157]
Pavement
[156]
Roofs
[150]
Garden
[158]
Petrol
Station
[159]
Auto
Dismantler
[159]
Ammonia (mg.L-1
)
0.5 0.19
Arsenic (mg.L-1
) 0.0084
Cadmium (mg.L-1
) 0.0009
< 0.002
0.0005
Calcium (mg.L-1
) 12.7 12.16 2.45
Chemical Oxygen Demand (mg.L-1
) 49.5 14.2
310 634
Chloride (mg.L-1
)
3.64 12.1
Chromium (mg.L-1
) 0.0088
0.0059
Conductivity (us.cm-1)
72.48
Copper (mg.L-1
) 0.0513
0.08 0.0781 0.0638
Fecal coliforms 6083 MPN.100mL-1
218 cfu.100mL-1
Glyphosphate (pesticide, mg.L-1
) 27.8
Lead (mg.L-1
) 0.0796
0.014 0.045 0.0028 0.0296
Magnesium (mg.L-1
) 3.2 0.8
Nickel (mg.L-1
) 0.0101
0.0248
Nitrate (mg.L-1
) 1.1 0.721 0.23
70
Table 3.3 cont Typical stormwater runoff qualities from different surfaces.
Parameter Roads
[157]
Pavement
[156]
Roofs
[150]
Garden
[158]
Petrol
Station
[159]
Auto
Dismantler
[159]
Nitrite (mg.L-1
) 0.1 0.086 1.16
Oil and Grease (mg.L-1
) 10.6
pH 7.3
5.65
Sodium (mg.L-1
) 11 2.85 8.4
Sulphate (mg.L-1
) 4.2 6.44 6.79
Total coliform 21970 MPN.100mL-1
542 cfu.100mL-1
Total Dissolved Solids (mg.L-1
) 184.1
97.9
Total Hydrocarbons (mg.L-1
)
1.2 12
Total Kjeldahl Nitrogen (mg.L-1
) 2
Total Nitrogen (mg.L-1
)
2.15
0.9
Total Organic Carbon (mg.L-1
)
4.42
Total Phosphorus (mg.L-1
) 0.3 0.114
Total Suspended Solids (mg.L-1
) 148.1
4.94
125 378
Turbidity (NTU) 310.1
Zinc (mg.L-1
) 0.2034
0.22 0.3784 0.2838
71
Bushland will contribute probably the least contaminated water of all runoff sources. In
forested areas, phosphorus and nitrogen compounds are effectively filtered by the
vegetation and without the heavy use of fertilizers contribution from these compounds is
quite low [149]. Leached salts and organics from leaf litter are also quite low [160].
Industrial sites are generally considered to be detrimental to water quality in a
catchment area. They can contribute high loadings of potentially unknown or unexpected
compounds. Having said this, larger industrial sites would be required by the
Environmental Protection Agency to capture all rainwater from the site for treatment
prior to disposal and only smaller sites are likely to contribute. While these are often
easy to separate from residential catchments, some like petrol stations and auto works
are often present within residential catchments. A study by Gnecco and co-workers
[161] has shown increased levels of suspended solids and hydrocarbons from such sites.
The auto dismantled in particular saw elevated levels of these compounds as well as
metals zinc, copper and lead.
The concept of first flush and removal of a small volume of stormwater collected at the
beginning of a storm is a well known concept in recycling. First flush is essentially
defined as the initial period of a storm event where the mean concentration during the
period significantly exceeds the event mean concentration. However, there are
significant questions that have been raised over the applicability of the first flush concept
to all contaminants. While some compounds show definite effects of first flush, others
show no significant difference in concentration over time [118, 161]. It is believed that
this is due to larger particulates that require larger volumes to be dislodged or released
[118]. Regardless, removal of the first flush in not recommended by the Australian
Guidelines as an effective technique for decreasing contaminant loads [5].
Stormwater base flow comes as a contribution from ground water or excess moisture in
the surrounding soil. It will often be of high mineral content, but could also contain local
contaminants from the water table. An understanding of pollutants may have entered
the water table will be of importance where infiltration into the storm water system is
high. Sea water infiltration may also be a possibility at coastal sites where groundwater
have been over-abstracted.
Biological contamination will come in two main forms, enteric bacteria and viruses
primarily from faecal sources and opportunistic bacteria that are present almost
everywhere. A major point source for enteric bacteria will be sewage treatment plants
(STPs). The Australian Guidelines for Recycled Water strongly recommends that STPs not
be present in stormwater catchments being used to generate recycled water [5]. Non-
point sources will include faecal matter from pets and other animals in the area and
generally cannot be avoided. Opportunistic bacteria are also a concern due to the
common use of aerosols during irrigation and the general potential for human
involvement in the irrigation process. Potentially lethal species such as legionella and
klebsiella may be present in storm water and skin irritants including the Pseudomonas
species are known to dominate in rain water tanks [94]. Treatment to reduce and
remove biological contamination will always be necessary when looking to reuse
stormwater.
72
3.3.3 Treatment
The first step towards “treatment” or improvement of stormwater quality actually comes
within the catchment. There are a number of steps that may be taken to partially treat,
or at least improve the quality of, storm water as it passes into and through the
stormwater collection system. Where performed correctly, street sweeping helps remove
metals and particulates that have deposited on the roads and in gutters and ultimately
reduces the impact of “first flush” (the higher concentrations of some species seen in the
early stages of stormwater collection).
Pretreatment processes focus on the removal of large contaminants such as litter (both
natural and artificial) and large particulate matter that will interfere in downstream
processing. On a small scale this can be performed using litter baskets or baffled pits to
separate litter. It can also be performed on a large scale using trash racks or gross
pollutant trap [162]. Please refer to the necessary guidelines for more information on
these techniques [162].
Swales and bioretention swales can be built into the side or median strip of a road to
provide some pretreatment for stormwater [162]. The swale itself is a vegetated
depression that can help retard water flows and allows for some basic sedimentation of
coarse particles. Bioretention uses a filter medium (typically a fine soil such as sandy
loam or coarse sand) to provide further filtration. The most important component
however is the presence of plants growing in the medium that helps slow water
movement and establishes a biofilm that can help in the biological treatment of water
removing some pollutants and nutrients. The design of these systems depends partially
on the characteristics of the area and what is needed in terms of treatment of
pretreatment. The aim of swales in general is to provide some retardation of water flows
and they are generally designed with this in mind. Otherwise they may be used as a
technique to provide some treatment prior to aquifer storage or as part of a conveyance
system. Design considerations can be found in documents from the CSIRO [162, 163].
Probably the most common form of treatment for stormwater is wetlands-based
treatments. These are used to mimic natural environments and primarily focus on
removing suspended solids, nutrients, and to a lesser extent organics, from stormwater.
A wetland treatment system consists of at least two (generally three) main areas [98].
The first in the inlet zone, which will be a deep water pond to collect particles in the size
range of sand and silt [98]. This area is generally permanently inundated. The second
zone is the macrophyte zone. This is the area that is highly vegetated and should
undergo periods of flooding and drying. This area will remove some of the finer particles
and soluble pollutants through physical and biological means. It is very important that
this zone undergoes regular drying and is not permanently inundated as this is how
macrophyte zones exist naturally, and ensures that the wetlands operate at maximum
efficiency.
These two zones are all that is needed for stormwater treatment, however a second
deep water area is often added to increase the residence time of water passing through
the system and encourage some further water treatment. This zone may also act as a
permanent storage area from which treated stormwater could be effectively collected.
Recommendations from the CRC for Catchment Hydrology in Australia recommend using
a riser (a partially permeable wall that allows slow flow of water down to a preset
storage height) to standardise the retention time throughout the process [98]. In
73
general the riser should maintain a permanent storage of between 10 and 15% of the
total storage. This allows for regular drainage of the macrophyte zone and best
performance from the system. For more information on design practices for wetlands
treatment please refer to the following reports and guidelines:
• Water Sensitive Urban Design Engineering Procedures: Stormwater (CSIRO
Publishing) [163]
• Urban Stormwater: Best Practice Environmental Management Guidelines (CSIRO
Publishing) [162]
• Managing Urban Stormwater Using Constructed Wetlands (CRC for Catchment
Hydrology) [98]
The storage of recycled stormwater from wetlands treatment can lead to potential
problems from potential water degradation by native wildlife. Generally native wildlife is
encouraged to wetlands areas as they can assist in the processes that occur and keep
nuisance species, such as snakes and mosquitoes to a minimum. Large quantities of
local wildlife can however lead to degradation in water quality particularly nutrients and
this should be considered when designing a storage system.
Pond detention is also used in stormwater treatment, but it is not necessarily as efficient.
Generally ponds with longer retention times would be required to ensure the same
pollutant removal efficiencies [98].
Natural processes rely heavily on the microbial breakdown of nutrients and organics in a
water stream. Two of the important processes are nitrification and denitrification. These
two processes are the backbone of biological nutrient removal. Nitrification ultimately is
the process of oxidising ammonia to nitrite and nitrate, while denitrification reduces
nitrate to nitrogen gas. The concern in stormwater treatment comes from the production
of the greenhouse gas nitrous oxide N2O (during both the nitrification and denitrification
processes [164]) in much larger concentrations than seen in natural wetlands [165,
166]. Nitrous oxide has a greenhouse gas potential 296 times higher than carbon dioxide
[167] and is a significant concern in wastewater treatment. The potential impact of N2O
and it formation should be considered as part of any stormwater treatment process.
The other greenhouse gas concern comes from the breakdown of organic pollutants in
stormwater and naturally occurring in the wetland. Deep water tends to be low in oxygen
and leads to the formation of anoxic zones in both the water and the soil where microbial
populations tend to produce methane when breaking down organics [167]. Shallow
waters have higher oxygen concentrations, and when dry reoxygenate the soil, resulting
in aerobic microbes breaking organic compounds down to carbon dioxide. Methane has a
greater greenhouse gas effect than carbon dioxide (about 23 times greater on a mass
basis [167]).
Other means of treatment tend to focus solely on particulate removal [163]. In this
respect sand filtration is the more common treatment technique [162]. This will remove
particulate forms of metals and nutrients, and may help bind some phosphates, but
unless slow sand filtration is employed (this technique also has a biological component),
there will be no significant reduction. Whether metals exist in a solid or soluble form
depends very much on the catchment characteristics. One of the more important
properties is the pH that can be easily altered by the presence of different surfaces.
Concrete and cement tend to result in a significant increase in pH due to the dissolution
74
of alkaline materials in the cement [118]. Asphalt on the other hand does not alter the
pH as dramatically (it is still slightly acidic) and consequently results in a different
partitioning of metals between solid and dissolved forms.
3.3.4 Inherent Advantages
While stormwater is climate sensitive, the large catchment areas typically employed
means they represent a significant water source under most circumstances. While it may
contain significant levels of pollutants, it can also be a source of nutrients for irrigation
water. Diversion of some of this water to irrigation will help to reduce pollutant loads in
local water courses. Importantly, increasing demands by the Environmental Protection
Agency may mean this water needs treatment prior to bay-side or watercourse
discharge. This means that some of the treatment that may be necessary for stormwater
recycling could already be in place. On the other hand, providing treatment for
stormwater recycling will have the added bonus of reducing pollutant loads from
discharged stormwater.
3.3.5 Potential Disadvantages
One of the biggest disadvantages to stormwater recycling is its general dependence on
rainfall. While base flow will be present its contribution may not e particularly significant.
This is important to treatment processes particularly those that rely on biological
processes. These typically require relatively regular flows (i.e. rainfall distributed evenly
across the year) or the technique can actually release more nutrients. This has
particularly been seen in poorly designed wetlands and reed-bed treatments [168].
Wetlands treatment in Adelaide utilizes groundwater to provide flows to the wetland
where stormwater supply is insufficient [100]. This, or some similar arrangement, should
be established as part of the planning of a wetlands treatment scheme. The impact of
evaporation on water storage and within wetland treatment systems also has the
potential to concentrate nutrients deliberately being withheld from rivers and other
watercourses. Specifically this can lead to cyanobacterial blooms. Water that has been
contaminated with cyanobacteria cannot be used for irrigation due to the significant
health risks posed. Such cyanobacterial blooms have been witnessed in stormwater
treatment systems in the Greater Melbourne area over the past few years. Algae, while
not presenting a human health risk, may result in chemical changes in the water, such
as introducing surfactant, which can be detrimental to the microbiology in the soil
associated with nutrient transformation and ultimately turf grass health.
The potential impacts of stormwater use are probably also the least understood. Most
research to date has focused on other water sources for reuse, while stormwater
research is more heavily focused on reducing nutrient loads in receiving waters. While
more studies are starting to become available a greater understanding of micropollutants
(i.e. pollutants that are present in very low concentrations)
75
3.3.6 Conclusions
Storm water can be a useful water source with a moderate to high level of nutrients that
can be made available during irrigation. While its direct reuse is generally not possible
without clear procedures to manage potential microbial issues, treatment can be cheap
and effective. The treatment comes with the added benefit of reducing nutrient loads in
discharges to sensitive water courses. The larger catchments typically mean stormwater
could probably provide the irrigation requirement for a sports field or come very close.
However it is still a climate sensitive water source, and drought or prolonged dry spells
could negatively impact on the operation of some treatment techniques. Plans should
made to combat this situation should it arise.
3.4 Recycled Water (Grey Water)
3.4.1 Introduction
Grey water refers to wastewater collected from around homes excluding water used in
the toilet. The exclusion of toilet water is designed to reduce biological loads in the water
and hence decrease the treatment (and often oversight) necessary in full black water
recycling systems. This makes grey water reuse quite attractive in new developments,
particularly for irrigation purposes. In larger sportsgrounds which may include shower
blocks and canteens or kitchens the flows from this type of water may make it of
interest. Decentralized treatment systems that separate toilet water from other
residential wastewater may be possible, however they are unlikely to be feasible when
full decentralized treatment of black water is also an option. With this in mind, the
following discussion of grey water use may be of relevance only to fields with greater
levels of associated infrastructure.
3.4.2 Quality Issues
3.4.2.1 Chemical
Untreated grey water qualities rely partially on the process from which they are sourced.
Grey water may come from bathrooms (showers and hand-washing facilities), laundries
and kitchens. Table 3.4 shows the water qualities associated with grey water sources
from different parts of the home. This data is generally sourced from Australia and can
be combined to give a rough guide of water quality from larger facilities. Variations in
qualities do occur largely due to the products used, but also due to water saving
initiatives that, while not necessarily impacting loadings, do result in concentration
increases due to lower water flows.
76
Table 3.4 Typical water qualities for grey water from different household processes.
Component
Source
Washing
Machine
[169]
Dish
Washer
[169]
Shower
[169]
Kitchen Sink
[169]
Vanity Unit
[169]
Toilet Block
[169]
Bathroom
[170]
Laundry
[170]
Alkalinity (mg.L-1
as a CaCO3)
19-60 19-220
Aluminium (mg.L-1
) 1.91 0.27 0.37 0.09 0.27 0.08 < 1.0 - 1.4 < 1.0 - 44
Boron (mg.L-1
) < 0.02 < 0.02 < 0.02 < 0.02 < 0.02 0.09 < 0.1 < 0.1 - 0.6
Cadmium (mg.L-1
) < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 1 < 0.01 - 0.05 < 0.01 - 0.05
Calcium (mg.L-1
) 7.17 11.73 7.68 8.73 83.59 15.46 2.7 - 8.6 2.3 - 12
Chromium (µg.L-1
) < 5 < 5 < 5 < 5 < 5 < 2
Cobalt (µg.L-1
) < 5 < 5 < 5 < 5 < 5 1.08
Copper (mg.L-1
) 0.17 0.811 0.121 0.268 1.39 0.471 < 0.05 - 0.32 < 0.05 - 0.49
Fluoride (mg.L-1
) 0.995 0.992 0.76 0.844 1.4 < 0.1
Iron (mg.L-1
) 0.09 0.121 0.11 0.146 0.19 0.546 < 0.05 - 8.0 < 0.05 - 4.2
Lead (mg.L-1
) 0.5 0.56 < 0.01 0 0.03 0.0046 < 0.05 < 0.05 - 0.48
Magnesium (mg.L-1
) 1.47 1.628 2.132 2.631 2.4 5.58 1.2 - 2.3 0.7 - 5.3
Manganese (mg.L-1
) < 0.0002 < 0.0002 < 0.0002 < 0.0002 < 0.0002 < 0.1
Molybdenum (mg.L-1
) < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 2.61
Nickel (mg.L-1
) 0.0016 0.032 < 0.003 < 0.003 < 0.003 < 0.003
Oil and Grease (mg.L-1
)
10 - 180 8.0 - 170
pH
6.4 - 8.1 6.3 - 9.5
Potassium (mg.L-1
) 5.8 13.23 < 0.01 11.8 5.4 92.08 1.3 - 5.2 1.1 - 23
Sodium (mg.L-1
) 116.6 260.6 13.47 40.1 26 87.23 7.4 - 29 12 - 480
Suspended Solids (mg.L-1
)
34 - 380 26 - 400
Total Dissolved Solids (mg.L-1
)
52.5 - 160 53 - 563
Total Kjeldahl Nitrogen (mg.L-1
) 5.45 16.7 5.02 10.9 13.34 276.7 2.4 - 23 1.0 - 40
Total Phosphorus (mg.L-1
) 0.22 12.18 0.26 2.2 64 50.06 0.1 - 0.88 0.062 - 42
Zinc (mg.L-1
) < 0.01 < 0.01 < 0.01 < 0.01 < 0.01 < 0.2 0.13 - 13 0.1 – 11
77
Bathroom
Water from the bathroom will typically have a high sodium concentration due to the
sodium content of soaps and other personal care products [95]. Cleaning products such
as bleaches will also contribute to the load of sodium from these areas. Of greater
interest, particularly at sportsfields, could be the loadings of zinc that are attributed to
the washing off of sunscreen in the shower and with hand-washing [95], however zinc
concentrations generated in grey water in a typical home are similar to the incoming tap
water [169].
The type of soap used will also impact on water quality, with solids soaps contributing
more solids and organic content than liquid soaps [171]. Different soaps may also
impact on the salt concentrations/loadings in the final water quality. Toothpastes and
metal abrasion from electric toothbrushes do contribute measurable quantities of metals
to grey water, however they are not particularly significant [172]. Oil and grease
loadings from bathrooms are also quite significant representing half of loadings found
from a house [173].
Kitchen
Food scraps and dishwashing contribute significant loads of nutrients, some metals (such
as zinc) [169] and significant quantities of oil and grease (roughly a third of all oil and
grease from grey water) [173]. Poor water quality (high nutrients and grease and oils) is
often a justification for the exclusion of kitchen wastewater from grey water recycling
systems [174]. Detergents can contribute significant sodium content and some contain
high levels of phosphates [169]. Low phosphate detergents are available, however
anecdotally these are not seen to give as good a clean in dishwashers and there is some
opposition to their use.
Investigations into the use of untreated kitchen grey water for long-term irrigation in
Israel, specifically investigating the impact of oil and grease of irrigated soils have found
significant concentrations of oil and grease in the top 20 cm of soil [113]. However, the
soil did not show any significant water repellence. It was theorised this was due to the
additional presence of surfactants that may have acted as a bridge, limiting the
hydrophobic impact of the oils.
Laundry
Grey water from laundries can be variable in quality and daily quantity as clothes washes
are not necessarily performed regularly, but only when a load is generated. The main
contamination of the water comes from the materials accumulated on clothes. In terms
of product choices, laundry powders contribute greater salt loadings than liquids [95]
and front-loaders contribute higher nitrogen and suspended solids concentrations than
top-loaders [95]. Some laundry detergents may use significant levels of phosphates,
however this is decreasing over time as reformulations occur [95]. Similarly historically
high levels of boron in grey water from detergents [16, 170] have now been all but
eliminated [169].
78
3.4.2.2 Biology
Biological contamination of grey water comes from two main sources: faecal
contamination and contamination from food. Faecal contamination comes primarily from
laundering of contaminated clothing (nappies etc.) and from showering [175].
Contamination from food focuses on bacterial species such as Campylobacter and
Salmonella [176]. These are enteric pathogens that may be ingested as part of
aerosolized irrigation water. Contamination of grey water may come from the cleaning of
food preparation surface and the cleaning of towels used for this purpose. Cross
contamination is common where only detergent and water are used to clean [177].
Disinfecting surface using sodium hypochlorite solutions (bleach) has been shown to
decrease the presence of bacterial species more effectively [177] and may lead to lesser
contamination in grey water. However, even with reduction, regrowth is still possible.
The high nutrient and organic loads that can occur in grey water and potentially elevated
temperatures depending on dominant sources encourages the growth of bacteria in grey
water storages and treatment systems prior to disinfection [174]. The risk of regrowth
and particularly the level of viruses, imposes the need for disinfection of grey water
[175].
3.4.3 Treatment
There are a large range of available techniques available for the treatment of grey water
streams [174]. The treatments can be quite similar to those used in sewage treatment,
although the demands on them are not necessarily as high. As such they can be divided
into three processes: physical treatment, biological treatment and disinfection.
Pre-treatment is an important part of any grey water treatment system. Here large
solids (e.g. food scraps) are removed and the oil and grease content can be reduced
[174]. Pre-treatment may use very coarse filters or screens, but can also use a septic
tank [174] where large solids settle and insoluble oil and grease float to the surface.
Further microbial processes may also occur here depending on the residence time.
Physical treatments typically involve either allowing particulate matter to settle from the
wastewater stream, or using a filtration to separate particles. At the less expensive end
of the treatment processes are the sand and soil filters. The generally coarse nature of
sand used for and filtration will remove significant fine particulate matter and some oil
and grease from a wastewater stream at a relatively fast rate. Soil filtration on the other
hand occurs much more slowly, however this means the biofilms can form and instigates
some biological treatment as well as filtration [174]. This means that the nitrogen
content of the water can be significantly reduced [178]. Also, the nature of soil means
that entrapment of phosphates is far more effective than in sand filters and significant
total phosphorus reductions can be achieved [178].
Settling can be inexpensive, however it is typically supplemented by chemical
coagulation and flocculation which can add significantly to the expense. The focus again
is on physical removal of particulates and some organic matter. The total phosphorus
and total nitrogen contents are largely unaffected and the nutrient value of the water
typically remains [174].
79
The other class of physical treatment revolve around membranes. Ultrafiltration is
typically used to remove particulates and some organic matter from the water, while
retaining high levels of nutrients [179]. One decentralized grey water plant in Germany
utilized this technique specifically to generate water for irrigation [179]. Other
membrane filtration techniques such as reverse osmosis can also be used. RO is able to
effectively remove salts where this is a concern, however it is very energy intensive and
ultimately expensive to run [180].
Biological treatments are also used in grey water treatment, largely for nutrient removal
to help discourage regrowth on microorganisms in storage or in the delivery system.
Common treatment techniques at the small to medium scale include rotating biological
contactors, sequencing batch reactions, membrane bioreactors and constructed wetlands
[174]. Biological treatment is generally followed by some filtration process and
disinfection to ensure high quality water is produced [174]. Biological treatments are
typically based on either aerobic processes or a combination of aerobic and anaerobic. In
the aerobic stages, organics are reduced primarily to carbon dioxide and ammonia is
converted to nitrates. Anaerobic stages can then be used to convert nitrates to nitrogen
gas. Some biological phosphorus removal can also take place at this stage [181].
Rotating biological contactors (RBC) use a partially submerged support (on which
microbes are grown) that slowly rotates in a tank through which the wastewater flows.
The constant submersion and re-exposure to air allows keeps the system to maintain
aerobic conditions in a smaller space and for lower power usage than other systems
[181]. This makes it particularly attractive for small scale grey water treatment. The
nature of RBCs means that while they remove organic contaminants they will also reduce
the phosphorus concentration to some extent [182], meaning the nutrient value of the
water is decreased. When combined with UV disinfection, RBCs have been shown to
produce water of sufficient quality for toilet flushing in Germany [183]. In terms of cost
an Israeli study has shown that RBCs can be economically viable at 1.9 ML.yr-1
treatment rates [184].
Sequencing batch reactors (SBR) are, as the name suggests, a batch treatment
technique. Water is collected and, once enough is present, it is transferred to the reactor
tank where it undergoes biological treatment, is allowed to settle and the clean water is
removed [181]. It is very similar to traditional activated sludge treatments used in
sewage treatment, but has a smaller footprint and generally requires less capital
investment [181]. The flexibility of SBR is of particular interest as it can easily be
adapted to different treatment flows and changes in unit processes [181]. It is, however,
more complicated in terms of control making it somewhat unattractive [181].
Membrane bioreactors (MBR) combined the traditional sewage treatment technologies of
activated sludge treatment with membrane filtration [185]. This means that effective
solids removal can be achieved coupled with biological treatment (removal of organics
and some nutrients) in a small footprint [186]. MBRs are probably the most efficient
systems with regards to removal efficiencies [174], however they require significant
amounts of energy and have high capital and operating costs [186]. The same Israeli
study investigating RBCs found that MBRs were only economically feasible when
treatment rates exceeded 10 ML.yr-1 [184].
Where space is available, wetlands treatment is generally considered a good option due
to its low maintenance requirement and high visual amenity [98]. Constructed wetlands
80
treatments for stormwater were discussed in Section 3.3.3, however in grey water
treatment a different approach is generally required. Constructed wetlands can provide
both physical and biological treatment via sedimentation in the first flooded zone,
filtration through the macrophyte (shallow vegetated) zone and biological treatment,
primarily in the macrophyte zone but also in the final storage lake [98]. Importantly,
wetlands treatment relies heavily on the periodic flooding and drying of the macrophyte
zone [98]. While the periodic flows of water generated by storm events are ideal in
generating this for stormwater treatment, grey water flows are quite constant and
consequently need a different approach. While stormwater treatment tends to use
surface flow wetlands, for grey water and sewage treatment the use subsurface flow
seems more common [187, 188]. By this it is meant that the water to be treated flows
through the soil of the vegetated area rather than over the surface [181]. This gives
additional benefits in that exposure to the potentially higher bacterial loads present in
grey water is minimised [181]. Issues related to odour and mosquitoes are also
minimized [181]. However, the costs of such systems can increase significantly [181]
due to the need to import a soil with a percolation rate that is sufficient for treatment.
Disinfection is almost always required for grey water treatment. This is to achieve the
final log reduction requirements as set out by the Australian Guidelines for Recycled
Water [5]. Section 2.2.6.5 outlined the general disinfection techniques used in recycled
water streams. For grey water UV technology seems to dominate in terms of use [183,
187, 189] probably because does not require significant chemical storage. UV irradiation
is successful in removing microorganisms, however it does not prevent regrowth, which,
due to it nutrient content, is commonly cited as potential for concern in grey water
recycling [186]. Chlorination would be more effective in this respect as it leaves a long
lasting residual. However it may suffer from interferences if the organic content is high
[125]. One new product utilizes stabilised hydrogen peroxide as a disinfectant. On a
small scale this may be more suitable for disinfection that chlorination [190].
With the exception of constructed wetlands, it is unusual to see one technology used on
its own. Typically a treatment train is established utilizing selected units described
above. Some treatment trains that are used include:
• Sand filtration followed by membrane filtration and disinfection [174].
• Screening followed by sedimentation and disinfection [191]
• Filtration followed by activated carbon treatment (to adsorb organics), sand
filtration and disinfection [192]
• Rotating biological contactor followed by sand filtration and chlorine disinfection
[182]
Ultimately the treatment train that is chosen is dependent on local conditions such as
space, the flow rate needing to be treated, the desired product water quality and the
level of maintenance and labour that can be dedicate to the plant.
81
3.4.4 Advantages
Grey water has a reasonable nutrient value, particularly phosphorus, that is valuable for
irrigation purposes. The presence of surfactants can also be valuable as they traditionally
help with soil wetting [193]. While treatment will remove some of these compounds
there will be some residual that will be of value. Some of the nutrients that are removed
will become available through sludges as biosolids for fertilization, depending on the
treatment technique used. Fertilization with biosolids can easily provide the necessary
micronutrients to suit a turf’s needs [9].
While it is sometimes debated, it is generally believed that microbial contamination of
grey water is not as significant as in sewage [174]. The average values used in the
development of the Australian Guidelines for Recycled Water supports this view [5].
Water availability for grey water is generally more constant and reliable than rainwater
or stormwater and storage volumes could potentially be reduced. This would bring
significant cost benefits.
3.4.5 Disadvantages
While the sizing of tanks may bring some costs benefits, overall costs can be particularly
unattractive. Decentralized systems that are of an appropriate size for sports ground
irrigation are going to incur costs, not just in building the plant, but also doubling the
infrastructure to convey source separated grey water. The added cost can quickly make
a project unattractive when considered from a retrofit point of view.
Another disadvantage is the potential for high presence of salts, particularly sodium,
from products used in the households or local facilities. This has the potential to become
damaging to turf and soil if it is not monitored. Calcium additions may be required on
soils where sodium content is high. Otherwise the high energy reverse osmosis could
also reduce the high sodium content.
3.4.6 Conclusions
Grey water as a less contaminated water would seem attractive as a potential irrigation
source. While nutrient levels are reasonable they are not excessive and only treatment
for the reduction of microbes may be required. The main hurdle to grey water use at the
moment is in terms of unit costs and space allocation. Where space if available, wetlands
treatment would be suitable, however where minimal space is available small footprint
biological treatment systems are generally quite expensive and need larger flow rates to
justify them.
82
3.5 Recycled Water (Black Water)
3.5.1 Introduction
Black water is ultimately sewage. It includes all wastewater from within a house,
commercial or industrial premises. It can vary significantly in terms of quality based
around the characteristics of the catchment. Higher levels of contamination typically
come from industrial sources, while ground water infiltration will lead to changes in salt
concentrations. While there can be a seasonal variation in volumes, the more significant
impact comes during wet weather when illegal storm water connections can significantly
increase the flow of water. While this does little to the concentrations it does place stress
on any treatment process that is put in place.
Recycled water can also be generated in a number of ways: via centralized treatment
plants, decentralized treatment plants and sewer mining. In general the difference
between these is the scale on which treatment is provided. Examples of centralized
treatment include Western and Eastern Treatment Plants in Werribee and Carrum
respectively. These plants can provide recycled water on a large scale often meaning
they can be more economical, however they have less control over the catchment and
therefore typically have high levels of industrial input leading to higher salt and metals
contents. Table 3.5 shows typical recycled water qualities from both Eastern and
Western Treatment Plants. Decentralized systems are smaller, typically encompassing a
small town or suburb. The lower flows can make the economics of treatment less
favourable, however there is greater control over the catchment and it is possible to
minimize industrial inputs. Finally sewer mining is probably the smallest scale in terms of
recycled water production, making water production quite expensive. It also has little
control over the catchment as it is typically an afterthought in the development of a
sewage system. It does have a very small physical footprint and can be installed almost
anywhere there is a sewer main nearby. This is typically seen as its most important
advantage.
The requirements for treatment generally depend on the biological removal and are
defined in the Australian Guidelines for Recycled Water [5]. However, the current
Victorian EPA guidelines are different and it is common for water authorities and
professionals to refer to Classes of recycled water. The definitions of these Classes are
shown in Table 3.6. Typically Class A water is used for irrigation of sports fields, however
Class B and C may be used where significant steps are taken to reduce access to the
field during irrigation. Readers are referred to the EPA documents for more information
[194].
3.5.2 Quality Issues
Recycled water from raw sewage can be variable depending on the source of water.
While residential sewage is generally consistent (keeping in mind the variability due to
product usage described in Section 3.4.2), industrial sources can bring about significant
variation. Table 3.7 shows the results of a study of sewage in Melbourne, specifically
identifying residential sewage quality. The data for industrial sewage has been derived
from this, however its reliability due to the significant variations that occur in industrial
processes is somewhat questionable. For decentralized systems operating in a purely
residential catchment the residential sewage quality is probably a good estimation.
83
Table 3.5 Typical recycled water qualities from Eastern and Western Treatment Plants in Melbourne
Parameter ETP Median
[195]
ETP Maximum
[195]
WTP Median
[196]
Alkalinity 155 190 -
Aluminium 0.26 0.9 < 0.05
Ammonia 12.6 18.6 -
Arsenic 0.002 0.006 0.002
Biological Oxygen Demand 0 5 < 2
Cadmium - - < 0.0002
Calcium 18.5 23 36
Chloride - - 430
Chlorine 5 5.7 -
Chromium - - < 0.006
Conductivity (uS.cm-1) 918 988 1900
E. coli (/100mL)
Iron 0.32 0.79 0.085
Lead - - < 0.001
Magnesium 9.4 11 26
Manganese 0.044 0.55 0.064
Mercury - - < 0.0001
Nickel - - 0.017
Nitrate 6.2 8.9 -
pH 7.1 7.2 7.4
Potassium 21 24 32
Sodium 100 110 290
Sulphur 64 65
Suspended Solids 1.5 14 5
Total Dissolved Solids 458 511 1200
Total Nitrogen 21 21 21
Total Phosphorus 8.1 28.7 -
True Colour (PtCo) 80 180 20
Turbidity (NTU) 0.2 3.5 -
Viruses (FRNA) < 1 < 1 < 2.5
Zinc 0.054 0.18 0.017
84
Table 3.6 Victorian EPA guidelines for pathogen levels in recycled water. Adapted from [123, 197]
Classification Requirements
A
< 10 E. coli per 100 mL
Viruses: 7-log reduction from raw sewage1
Protozoa: 6-log reduction from raw sewage1
< 1 virus particle in 50 L2
< 1 viable helminth egg in 1L2
< 1 protozoa in 50 L2
B < 100 cfu per 100 mL
Helminth reduction for cattle grazing
C < 1,000 cfu per 100 mL
Helminth reduction for cattle grazing
D < 10,000 cfu per 100 mL 1According to the Guidelines for Dual Pipe Water Recycling Schemes. This is more commonly used for the
definition of Class A water in Melbourne 2According to the Guidelines for the Use of Reclaimed Water
Table 3.7 Typical sewage qualities from residential sewage, industrial sewage and a mixed stream.
Adapted from [198].
Component Residential
Sewage
STP Influent
(mixed
catchment)
Industrial Sewage
Aluminium (mg.L-1
) 0.745 0.933 2.8
Ammonia (mg.L-1
) 36.2 39 60
Arsenic (µg.L-1
) 2.3 2.6 5
Barium (mg.L-1
) 0.038 0.167 2.378
Boron (mg.L-1
) 0.263 0.263 0.259
Calcium (mg.L-1
) 9.26 17.2 355
Chromium (µg.L-1
) 3.2 31 259
Cobalt (µg.L-1
) 1.28 1.75 6
Copper (mg.L-1
) 0.062 0.077 0.348
Iron (mg.L-1
) 0.728 1.23 7.998
Lead (µg.L-1
) 13 68 1159
Magnesium (mg.L-1
) 4.925 9.9 72.8
Manganese (mg.L-1
) 0.048 0.218 2
Nickel (µg.L-1
) 4.2 14.3 193
Oil and Grease (mg.L-1
) 22 59 351
Potassium (mg.L-1
) 16.78 22.45 70.13
Sodium (mg.L-1
) 87.28 137 567
Strontium (mg.L-1
) 0.05 0.0945 0.859
Tin (µg.L-1
) 4.69 6.7 23
Total Dissolved Solids (mg.L-1
) 375 550 2513
Total Nitrogen (mg.L-1
) 57 61 97
Total Organic Carbon (mg.L-1
) 173 271 1176
Total Phosphorus (mg.L-1
) 7.3 4.7
Zinc (mg.L-1
) 0.169 0.346 2.478
85
3.5.2.1 Salinity/Sodium content
One major cause for concern when recycling water from sewage is the salinity or salt
content. This is because traditional techniques have little impact on sodium
concentration. Sewers with high industrial inputs could suffer from elevated sodium
levels as a result of neutralization of industrial streams or typical processing waters. The
elevation of sodium in this case is significantly more than either calcium or magnesium
and it is possible for treated waters to have SARs in an unacceptable range for turf and
soil health [16]. Where an estimate is required one rule of thumb to estimate salt
concentrations in recycled water is to take the potable concentration and multiply by ten.
Ground water infiltration of sewers can also be significant, particularly in older or poorly
maintained systems. The chemical changes brought about by ground water infiltration
depend entirely on the local groundwater quality. While in most areas this will increase
the calcium content more than the sodium, sea water intrusion into ground water due to
over abstraction can lead to significant increases in the sodium content [199]. This is
turn leads to unacceptably high SARs for irrigation and care must be taken.
Due to problems with sodium content, it is generally recommended that recycled water
from municipal wastewater not be used for irrigation on clay soils and instead it should
be used only for sandy loams to sand soils [16].
3.5.2.2 Boron
Another major source of concern in recycled water is boron and the potential for boron
toxicity. In the past boron was used in a number of cleaning products [16]. However,
this has decreased substantially over time and the most significant source of boron is
now in faecal matter [169]. This is well below the recommended limits for boron and it
should not be a problem in a residential catchment [16]. Still, it is often recommended
to remove clippings from turfs irrigated with recycled water in order to minimise the
potential for the accumulation of boron in the soil [16].
Industrial contamination from boron is a possibility from some processes. This would,
however need to be assessed on a case by case basis.
3.5.2.3 Nutrients
Phosphorus and nitrogen are available in significant quantities in raw sewage due to their
high content in human extreta. While treatment will reduce these concentrations, some
content will remain. The use of recycled water for irrigation is considered beneficial as
the nutrients are provided more regularly than by fertilization [16]. There are claims that
using recycled water will provide all the phosphorus and potassium content a turf will
need [16], however this can be variable depending on the turf and soils used.
While the presence of nutrients is generally positive, overapplication can be a concern.
One particular concern is nitrogen that has been flagged as providing 2-3 times the
requirements in some recycled water sources [200]. The form of phosphorus and
nitrogen applied during irrigation tend to be soluble and not all are entrapped within the
turf. It is possible to washout some of the applied nutrients. This is potentially damaging
to local waterways and must be carefully regulated.
86
3.5.2.4 Alkalinity
The alkalinity of recycled water can be quite high. The impact of this on turf comes
through changes in the soil pH and ultimately the microbial populations there [16]. The
microbes are important to the conversion of nitrogen compounds to more suitable
products for plant uptake. Alkalinity in the form of carbonates can also lead to deposits
forming on the leaves of turfgrass. High alkalinity therefore is undesirable. The
bicarbonate concentrations should be maintained below 90 mg.L-1 and definitely below
500 mg.L-1 [16]. Where this is not possible it addition of an acidic compound may be
required.
3.5.2.5 Metals
In terms of metals, only two of the raw sewage concentrations in a mixed catchment
trigger the trigger the long-term irrigation values specified by the Marine and Fresh
Water Quality Guidelines [106] and may need to be monitored. These are iron and
manganese. In general treatment process will reduce these somewhat. Manganese levels
only just reach the trigger value and are unlikely to be a significant concern. Iron on the
other hand could be significant, although it has been noted previously that small
concentrations of iron in irrigation water may be beneficial to a turf [9].
3.5.2.6 Free Chlorine
Free chlorine in recycled water could be a significant concern as it can be used in high
concentrations as part of the disinfection process. It is possible for the free chlorine
content in recycled water to exceed what is seen in potable water. Chlorine levels should
be maintained below 1 mg.L-1 although up to 5 mg.L-1 may only be moderately
damaging [16]. Chlorine can be reduced if required by the addition of sodium
metabisulphite. Where possible, disinfection using other techniques such as ozonation or
chloramination may be more appropriate.
3.5.2.7 Biology
Common pathogenic species found in raw sewage and recycled water were described in
Table 2.23 in Section 2.2.6.3. These are the focus of the Australian Guidelines for Water
Recycling and their removal is discussed in detail in Section 2.2.6.
87
3.5.3 Treatment
3.5.3.1 Pre-treatment
Pre-treatment involves simple techniques designed to remove large insoluble objects
from sewage. The two most commonly used processes are screening and grit removal.
Screening focuses on removing items such as paper, sanitary products and litter that
find their way into the sewers. Grit removal focuses on settling out the larger particles
from sewage. Both processes generate solid waste streams that must be disposed of
while also removing a portion of the incoming water.
3.5.3.2 Primary Treatment
Primary treatment focuses on physical processes for removal of contaminants from
sewage. Though it is considered a physical process it often employs the use of chemicals
such as ferric chloride or alum to aid in flocculation and coagulation processes. The
ultimate focus is to remove smaller particles by forcing them to combine into larger
particles and allowing them to settle to the bottom of the trough or tank. This is
generally combined with a small amount of grease or oil removal that can form a scum
at the surface of the water. In some parts of Australia this is the minimum amount of
treatment required for discharge of water to deep ocean outfall. It is not sufficient,
however, for creating irrigation water from sewage.
3.5.3.3 Secondary Treatment
Secondary treatments tend to revolve around biological processes for the reduction of
organic and nutrient contents is water. On a large scale these may include lagoon
treatments, activated sludge treatments or membrane bioreactors. These processes
typically use aerobic conditions to help convert ammonia to nitrates and organic
compounds to carbon dioxide. The processes are quite energy intensive due to the need
to pump air or pure oxygen into the water on a continuous basis [201]. Activated sludge
treatments may account for 70 % of a tertiary treatment plant’s electricity requirements
[201]. The process generates also tends to generate a large amount of other wastes
both solid and gaseous that will need to be considered. Solid sludges produced at this
point are generally high in nutrient content (removed from the wastewater stream) and
after treatment to remove microbial contaminants and to dry them out may be used as a
fertilizer. Gaseous products include carbon dioxide, nitrous oxide and methane, all of
which are greenhouse gases. The worst of these is nitrous oxide [167]. It can be formed
during the conversion of ammonia to nitrogen dioxide although the percentage is fairly
small.
While conventional techniques typically stop here, some processes will aim at further
nutrient reduction by adding an anaerobic stage. In this stage nitrates are reduced to
nitrogen gas and phosphorus may also be more effectively removed. This significantly
reduces the amount of nutrients available in the irrigation water which may be beneficial
where high nutrient content runoff and fouling of irrigation pipes are a concern. The
drawback is a significant increase in the production of greenhouse gases, particularly
nitrous oxide and methane.
88
3.5.3.4 Tertiary Treatment
Tertiary treatment typically refers to disinfection processes. Typically this involves
chlorination, but may also include ozonation or UV irradiation. Disinfection is an oxidative
process and also brings about a small reduction in the remaining organics. The Where
chlorination is used, care must be taken to ensure the residual is not too high for
irrigation (preferably less than 1 mg.L-1 [16]). While the other techniques may be less
toxic overall to plant life the main reason for this is their shorter half life and the fact
there is less or a short lived residual [125]. This in turn may lead to regrowth problems
where the water is stored for long periods.
3.5.3.5 Higher Treatment
Where salt and particularly sodium concentrations are elevated, higher treatments may
be required. These typically revolve around the membrane filtration technique reverse
osmosis. This technique, also used in seawater and brackish water desalination,
effectively removes most components from contaminated water streams. In recycled
water it is typically used to provide high quality water for drinking or sensitive industrial
processes such as steam generation and electronics manufacture [202]. This generally
means the water is over treated, however if the salt content is too high, the water
cannot be used otherwise.
Reverse osmosis processes can be very energy intensive when compared to other
sewage treatment processes (approximately 1.7 kWh per kL of produced water for a
brackish water process [203]). This significantly increases the production costs of water.
Also the membranes used are not tolerant of chlorine [204]. As a result it is generally
more economical to use secondary treated wastewater as a feed to higher treatment
processes than tertiary treated [202]. This water can also contain some suspended solids
that will foul and reduce the performance of RO membranes. To prevent this
microfiltration may be employed. This further increases energy consumption [205].
While the benefit of using advanced treatment is to remove unwanted salts, the process
will also remove nutrients and results in the formation of a concentrated stream of water
that must be disposed of. Though it is highly variable, a quick estimate of the water
losses would suggest that for every kL of water produced 250 to 670 L is lost (derived
from [206, 207]). The nutrient content will be reduced to at most 10% of concentrations
prior to RO [208]. While the nitrogen component may be lost, there is a possibility of
recovering phosphates separately, either by precipitation from the concentrate stream or
through the use of another membrane prior to RO. These technologies are still being
explored and commercialisation may not occur until sometime in the future.
3.5.4 Inherent Advantages
Sewage is a rich source of nutrients, both nitrogen-based and phosphorus-based. While
some treatment techniques can significantly reduce this, the benefit of local of
decentralized production is the availability of biosolids. If the catchment has been
properly managed and contains almost exclusively residential dwellings then biosolids
can be easily used as an inexpensive fertilizer for the sports field. Importantly trace
nutrients are also present in biosolids and this should ensure micronutrient deficiencies
do not occur [8].
89
In general, not all nutrients are removed during the treatment process, however. The
remaining nutrients will be delivered to the turf during irrigation. This will significantly
reduce the requirements for fertilizer use onsite. Research has estimated that
phosphorus application rates would be roughly equal to demand while nitrogen
requirements could easily exceed requirements in terms of fertilization [200]. According
to this study the average Canberra resident would contribute the equivalent of 50 kg of
Multigro fertilizer for one year and 100 kg of nitrogen. This compares to a recommended
application of 40 kg each year for 500 m2 of sports field.
For Melbourne, to estimate the mass of nutrient delivered in g.m-2.yr-1 the following
equation may be used:
��vGuI�GwGv � �q��z�q(L� o�
Where �q�� is the annual irrigation delivered in L.yr-1, z�q(L� is the area of the field is m2
and o� is the concentration of species y in g.L-1. If we were to assume an average sized field (1.7 ha or 17000 m2) with a water requirement of 3.5 ML.yr-1 (3500000 L.yr-1)
using irrigation water from Eastern Treatment Plant (oQ=0.021g.L-1 [195]), then 4.3 g.m-
2.yr-1 of nitrogen should be delivered to the turf through irrigation. Assuming a couch
turf this would provide the equivalent for one growing month. Increasing irrigation would
increase the nitrogen delivered and therefore the demand that may be met by irrigation
is highly dependent on the irrigation volume used for a field.
The availability of recycled water is another significant advantage. It is available at a
relatively constant rate, although there are slight seasonal variations. This makes any
treatment that may be needed easier to manage. The other possibility is that already
treated recycled water could be made available by the local water authority. This is
similar to a potable water system in that the water is generally available on demand,
giving a greater water security than weather-dependent sources such as roof water.
3.5.5 Potential Disadvantages
While recycled water is somewhat independent of climate and may be regarded as
drought tolerant, it is questionable whether it can be referred to as drought-proof.
During water restrictions, changes in consumer behaviour, both commercial/industrial
users and residential users, result in decreases inflows to sewage treatment plants, and
ultimately limit the amount of recycled water that can be produced. In some part of the
United States, over allocation of recycled water resources has meant that during times of
drought, even these water sources are often placed under restricted use. The possibility
of recycled water being restricted should be considered when developing a water
management plan.
While recycled water can be a useful source of nutrients, sometimes the nutrients are
available in concentrations that are too high either for the irrigation system or the soil.
Irrigation with recycled water has led to higher nitrogen and phosphorus in runoff [209].
Concurrently, the availability of phosphates in particular can lead to increased microbial
growth and ultimately biological fouling [5]. Nutrient removal or reduction is a possibility
during treatment processes, particularly through more advanced biological techniques or
reverse osmosis. It is possible to reduce the nutrient content sufficiently, while
maintaining some of the benefits of its presence.
90
Some of the controls placed on the use of recycled water can make its use restrictive.
Limiting irrigation times or practices may not be suitable to some sites or may increase
the financial burden of its use. At these sites recycled water may not suitable.
Salinity issues can also be significant in recycled water. Where the SAR is high, periodic
liming of the soil may be required, or addition of calcium salts to the irrigation water.
This is particularly important for clay rich soils as these are impacted more significantly
be saline waters [16]. Recommendations suggest recycled water only be used on soils
that have a texture of or sandy loam or coarser [16].
The final disadvantage is applicable specifically to sewer mining – access rights.
Negotiations over access to water from sewers cannot be considered a straightforward
process. Different water authorities are responsible for different sections of sewers within
Melbourne and extraction from some points will not necessarily be supported due to
potential impacts of sewers downstream of this point. These issues and the time
associated with overcoming them must be considered as part of the scoping of potential
projects.
3.5.6 Conclusions
The high nutrient content of recycled water is a significant benefit to irrigation. Some
authors have claimed that this will meet all of a turf’s potassium and phosphorus
requirements and almost all of the nitrogen. At a minimum it should significantly reduce
fertilizer requirements. Where a decentralized treatment system or sewer mining is
employed the generation of sludge/biosolids will have the additional advantage of
providing a mincronutrient rich fertilizer.
While salinity may be an issue with recycled water in some areas this can be mitigated
somewhat by further treatment, although this will come at increased expense. Where
salinity is high but not extreme the use of recycled water should be limited to sandy
loam soils and coarser, it should not be used on clay-based turfs.
3.6 Ground Water
3.6.1 Introduction
Ground water is included in this discussion as alternative water source. This does not
mean it is naturally sustainable. Sustainable use of ground water is difficult to ensure,
but essentially requires that water enter the aquifer at a rate equal to or greater than
that which it is abstracted. This may be achieved through aquifer storage (where a
treated wastewater is pumped into or percolated into the water table and later extracted
for use), or through aquifers that have a naturally fast recharge rate (however this
means they are dependent on rainfall and therefore not drought-proof). Ground water
sources can also vary significantly in terms of quality. Throughout the Melbourne region
ground water is very rarely used due to a lack of surface aquifers and due to increasingly
poor water qualities in those that are present. Sea water intrusion is also a significant
concern, particularly in the Altona region.
3.6.2 Quality Issues
91
Table 3.8 Typical water qualities from bores in the lower Dandenong Ranges. Adapted from [210]
Parameters Low elevation
basalt bore
Low elevation
sedimentary bore
pH 7.3 6.7
TDS (mg.L-1
) 435 537
Dissolved O2 (mg.L-1
) 8 <1
Ca (mg.L-1
) 37 26.8
Mg (mg.L-1
) 32 37.4
Na (mg.L-1
) 56 54.5
K (mg.L-1
) 4 1.8
Si (mg.L-1
) 18.6 25.6
SO4 (mg.L-1
) 6 < 0.1
Cl (mg.L-1
) 103.9 118
Br (mg.L-1
) 0.28 0.36
HCO3 (mg.L-1
) 177 230
The main chemical constituents of ground water are dissolved minerals, typically calcium
or magnesium based. Table 3.8 gives list some typical groundwater qualities from the
foothills of the Dandenong Ranges. High calcium content leads to a hard water, meaning
it is difficult to make a soap foam, but is preferential for irrigation over a sodium rich
water. In general the increased residence time of ground water (that the longer it takes
to flow, and ultimately, the lower in elevation it is taken from) the higher the TDS
content [210].
The local geology will have an impact on water quality in two ways. As noted earlier the
dissolution on minerals typically occurs in aquifers and as ground water drains. A study
in the Dandenong Ranges has looked at the two most common geological systems in the
Melbourne area tertiary basalt and Silurian-Devonian sedimentary rock [210]. The first
dominates in the west of Melbourne while the second dominates in the east. While basalt
based groundwater has a reasonable TDS, that of the sedimentary aquifers tend to be
higher where residence times are longer. Importantly the ratio of sodium to calcium in
the sedimentary aquifers tends to higher. Also of importance is the fact that basalt
groundwaters show signs of continuous infiltration of surface waters which would make
them more susceptible to contamination from practices occurring here.
Another important point to consider is the dissolved oxygen content. Ground water
aquifers are generally anoxic (i.e. free of oxygen) [100]. This controls the chemistry and
biology of the water within the aquifer. Under such conditions most species exist in their
reduced forms. That is to say that nitrates can be transformed to ammonia, sulphates to
more acidic sulphides and metals to their reduced state such as iron(III) salts to the
more soluble iron(II). One problem seen with ground water is the slow oxidation of these
reduced species that occur once the water is exposed to the atmosphere. This is one of
the reasons that aeration of ground water is typically practiced prior to its use [211].
The presence of dissolved metals can be a concern in this respect. Iron can be, and
generally is, present in high concentrations and some heavy metals such as arsenic and
selenium can also be an issue. While iron can be toxic to turf, its presence at low levels
can be beneficial [9]. However its presence in a reduced form that is then oxidised to the
less soluble iron(III) leads to precipitation in storage media or in pipes. This may not be
92
an issue where a sufficient residence time in a tank is used, but could lead to damage to
pumps and sprinklers if not properly treated. Aeration and oxidation of the water
followed by filtration or detention should reduce this impact.
Arsenic is present in a number of minerals around Australia and Victoria [212] and can
lead to leaching of arsenic into groundwater. There is a theory that as abstraction occurs
this is accelerated due to the oxidation and release of mineral arsenic in the aquifer
when water is replaced by air and subsequently rewetted [213]. In some areas this has
lead to problems with ground water use as a drinking water due to excessive arsenic
levels [214]. The concentrations may also be excessive for irrigation. Treatment may be
required to remove this species.
The other major point of concern in groundwater is contamination from infiltration of
chemicals from the sources. This contamination can come from point sources or non-
point sources. Examples of point sources include industrial sites [211, 215] and petrol
stations [216, 217]. These generally come from spills and leakages and can increase the
levels of unwanted heavy metals or organics. Petrol stations and the associated
underground storage tanks, in particular can contribute to increased refined petroleum
levels in ground water, leading to high levels of toxic benzene, toluene, ethylbenzene
and xylene [217]. In the United States this has led to these compound being the most
frequently detected compounds in drinking water supplied that rely on ground water
[217]. Where these facilities may be present in the charging zone for an aquifer,
particularly near the bore to be used, treatment or avoidance should be considered.
Non-point sources are more complicated. The most significant however is the infiltration
of nitrogen and phosphorus from fertilizer use in agriculture, gardens and open space
management [218]. This can be significant particularly where there is high rainfall [219].
Similar sources can also introduce pesticides and herbicides to groundwater [220] that if
significant enough will require some treatment to remove.
3.6.3 Treatment
As a minimum for groundwater aeration is often performed. This helps to remove
unwanted volatile compounds such as VOCs (including petroleum components) [217],
carbon dioxide [221] and hydrogen sulphide [222]. The process of aeration can also
assist in the oxidation of components such as iron and manganese, though this is
achieved more efficiently if an oxygen enriched stream is used [221]. The oxidation of
these species, coupled with the pH increase of carbon dioxide removal helps facilitate
precipitation. Subsequent filtration using sand filtration or microfiltration can then be
used to remove the precipitate [221].
Where salt contents are high, demineralization may be required. This can take the form
of either reverse osmosis or ion exchange. Reverse osmosis is effective at removing
almost all salts from solution. The main problem that could arise is with scaling of the
membrane which will increase operating costs as well as disposal of the concentrated
waste stream. While reverse osmosis is probably the most efficient technique for
removing sodium and chloride salts, scale formation from calcium-based salts is
common. Calcium carbonate or phosphate concentrations will generally limit the
recovery of water is such circumstances. While research is ongoing in improving
recovery where these compounds dominate [223], nothing has reached a commercially
93
viable state at this time. Consequently either low recoveries, or increased operating
costs must be expected.
The concentrated waste stream produced via reverse osmosis must also be disposed of.
While discharge to sewer may be an option, there are generally restrictions on salt
concentrations of streams discharge to here. This can make disposal costly in the long
run and ultimately make reverse osmosis of groundwater unattractive.
Ion exchange operates on the basis of adsorbing specific ions selectively from a water
stream. There is a limit to the amount of adsorption that can occur however, and
periodic regeneration of the ion exchange material is required. This will result in
increased operating costs due to chemical requirement and disposal [224], however it
can be more efficient where a specific component (e.g. arsenic) is targeted for removal
rather than all components in the water.
3.6.4 Advantages
Ground water can provide a relatively clean and high calcium-containing water that is
suitable for irrigation, but qualities vary significantly.
Where no or minimal treatment is required, storage is generally not an issue for
groundwater as the aquifer will act as a storage device. Recharging the aquifer with
treated waters is also an option. This would potentially reduce the cost, and more
importantly reduce the footprint, of storage of alternative water sources.
3.6.5 Disadvantages
Ground water is not necessarily sustainable. Care must be taken to ensure that the rate
of extraction does not exceed the rate of recharge. One step in doing this can be to use
the bore as a storage area for other alternative waters, such as storm water, that may
become available when they are needed least creating a long-term storage requirement.
Natural recharge is also climate dependent. The impacts of climate change are generally
expected to reduce recharge rates of ground water [225] and thereby making extraction
a less sustainable option. In some parts of Australia, historical over-abstraction of
ground water means this source should probably be avoided.
Ground water is also not available everywhere. It is highly dependent on the local
geology. Some aquifers are too deep to easily reach and this is the case in many parts of
Melbourne. Deeper aquifers also require more energy to extract from, making them less
sustainable overall.
Over abstraction of ground water can also lead to a decline in water quality over time.
This could mean significant changes in some components that ultimately make the water
unusable without further treatment. This is believed to be a particular problem with
arsenic where increased abstraction leads to oxygen entering the aquifer and forming
more soluble arsenic salts that can make their way into the groundwater that is
subsequently abstracted [213]. These types of changes should be avoided by minimising
abstraction and ensuring that abstraction rates do not exceed recharge.
94
3.6.6 Conclusions
While ground water can represent a clean and useful irrigation water, it must be
carefully managed to ensure sustainable use. Where natural recharge rates are lower
than water requirements, ground water abstraction should either cease or artificial
recharge should be initiated.
Ground water quality is generally sufficient for irrigation without much treatment,
however it is very location dependent and contamination of ground water from human
activities can impact on the ability to safely use groundwater.
3.7 Desalinated Water (Brackish Water and Sea Water)
3.7.1 Introduction
Sea water and brackish water both have high salt contents that are generally unsuitable
for irrigation without treatment. Sea water is sourced either as a surface water from a
bay of coastal area or from “beach wells”, i.e. sea water sourced from below the surface
[226]. The composition varies somewhat from site to site but Table 3.9 shows a
standard breakdown of sea water. Brackish water is less salty and is defined as water
with a total dissolved solid content of between 1000 and 10000 mg.L-1 [222]. It is
generally sourced from ground water, waste water and tidal mixes of salt and fresh
water that occur in estuarine rivers. This section will only consider the last of these with
ground water and wastewater discussed in Sections 3.6 and 3.5 respectively.
3.7.2 Treatment
In order for either brackish water or sea water to be suitable for irrigation some form of
desalination is required. On small scales this is typically performed using reverse
osmosis [180], although some thermal and charge based separations are also becoming
popular.
95
Table 3.9 Typical composition of seawater. Adapted from [227]
Parameter Concentration
Sodium (mg.L-1
) 10733
Chloride (mg.L-1
) 19344
Magnesium (mg.L-1
) 1294
Sulphate (mg.L-1
) 2712
Calcium (mg.L-1
) 412
Potassium (mg.L-1
) 399
Hydrogen carbonate (mg.L-1
) 142
Boron (mg.L-1
) 4.5
Total Nitrogen (mg.L-1
) 0.4
Total Phosphorus (mg.L-1
) 0.07
Copper (mg.L-1
) 0.0002
Iron (mg.L-1
) 0.00006
Zinc (mg.L-1
) 0.0004
Manganese (mg.L-1
) 0.00003
3.7.2.1 Reverse Osmosis
Osmosis is the process of water moving through a membrane from a more dilute solution
to a concentrated solution. In reverse osmosis (RO), the process is reversed by applying
a high pressure to the concentrated side and forcing water through the membrane to the
dilute side. The pores (or holes) in the RO membrane are small enough to prevent that
while water may pass through, the passage of salts is prevented resulting in a quite pure
water. Typical rejections, or removal efficiencies, for sea water RO are around 98-99.5%
[228, 229] and around 90-95% for brackish water [207]. The reason for the difference
lies in differences in the membrane and the need to optimize the rate at which water
passes through the membrane. There is also a difference between the rejection of
different ions and species, with ions like calcium, magnesium and sulphate having higher
rejections than sodium, potassium and chloride [207]. This can influence the quality of
the final water, depending on how the water was treated.
The amount of water recovered from RO processes depends on the quality of the water
being treated. For sea water this is limited to about 50 % [229] while brackish water can
range from 60 to 80 % [206, 207]. To achieve this recovery high pressures are often
required. For sea water desalination a pressure of at least 50 bar is required and often
operating pressures are higher [230]. Brackish water on the other hand needs a slightly
lower pressure (often 20 to 30 bar). The high pressures and low recoveries have a large
impact on energy requirements. Typical energy requirements are of the order of 4.5
kWh/kL of water produced for sea water and 1.7 kWh/kL of water produced for brackish
water production [203]. This energy requirement is significantly higher than other water
or wastewater treatment technologies and coupled with something like microfiltration
adds to the ongoing costs of seawater desalination. On the small scale typically required
for sports field or open space irrigation, the ongoing costs will easily be greater than the
cost of potable water. The energy requirements also contribute to the large carbon
footprint of the technology. This can be reduced by coupling reverse osmosis with
96
renewable energy sources such as photovoltaics [231, 232], wind turbines [231] or wave
power [231]. These have previously been proven on a small scale for brackish water
treatment in remote communities [233, 234].
Sea water RO can be operated in two modes, single pass or double pass. The two are
similar in terms of recovery [226] however the water qualities vary significantly [228].
Single pass refers to the fact the water is treated once, while in double pass the product
water (or permeate) from one RO is fed to a second RO unit to further reduce salt
concentrations. Quality variations are significant with single pass RO generating water
with a total dissolved solids content of 350 to 500 mg.L-1 [226, 228, 235, 236], while a
double pass system may produce a TDS as low as 2 to 11 mg.L-1 [228]. Other difficult to
remove components such as boron can also be more effectively reduced using a second
pass [228].
Another significant cost associated with reverse osmosis treatments is the disposal of the
waste stream. For low recovery sea water systems this may not be too significant as the
reject stream may not be too much more concentrated than seawater and disposal back
to the ocean or bay could be possible, assuming the necessary permits are granted. For
brackish water desalination the concentration increase is significantly greater making
disposal more complicated. While it may be possible to dispose of the water in the sewer
this would be dependent on the requirements of the local water authority. Otherwise
reject water would need specialist disposal.
3.7.2.2 Thermal processes
Thermal processes are typically more energy intensive than reverse osmosis, but can
produce a water with lower salt content. There are two main techniques that are utilized
for small scale desalination:
• Solar distillation – For small scale water desalination solar stills are often
recommended [180]. They operate by focusing sunlight on a pool of water
leading evaporation. The water vapours condense on the glass surrounding the
still and are collected. Aside from solar energy there are no significant energy
requirements making it particularly attractive. Having said this, its efficiency is
very low. It takes one day to produce 4 L from a 1 m2 plot [180]. On the scale
required for sports field irrigation, the size of a solar still would probably make it
unsuitable.
• Membrane distillation – While it was developed some decades ago, recent
advances in membrane technology have brought membrane distillation closer to
commercialization. The temperatures that can be used for membrane distillation
are generally lower than for other thermal processes reducing somewhat the
energy requirement. However, it is still more energy intensive than reverse
osmosis. This can be offset though by tying the technique with solar heating of
the water [231]. This has been successfully demonstrated in the past on both
large and small scales [231]. Geothermal treatment has also been effectively
used on a small scale [232]. The water produced by membrane distillation is also
of higher quality than what is seen by reverse osmosis [231, 232]. The most
significant drawback is the fact it is not yet commercialised making adoption of
the technology difficult, expensive and not without some risk.
97
3.7.2.3 Charge-based separations
One of the more typical charge-based separations is electrodialysis (ED). The technique
uses an electric field to separate ions and force them through selective membranes to
remove them from the water. To prevent precipitation the direction of the electric field
may be reversed every twenty minutes [231]. ED has been used for brackish water
treatment for some time and can be considered a mature technology [231].
The energy requirements of ED come from the applied electric field and the pumping
energy. It is typically seen as having a higher energy requirement than reverse osmosis
[231], with brackish water treatment typically needing 3 kWh/kL [205]. Integrating with
photovoltaics has occurred previously with success, though it is limited to brackish water
desalination [231].
3.7.3 Quality Issues
The quality of desalinated water is a function of the water used and the treatment
processes employed. As the main commercial technique for desalination the following
discussion applies primarily to water produced by reverse osmosis.
3.7.3.1 Issues related to the water source
Sea water around Port Philip Bay is particularly impacted by temperature fluctuation.
Temperatures from winter to summer can vary from 9 to 25 °C [237]. While salinity
fluctuations also occur (from 33 to 35 g.L-1 [237]) temperature fluctuations could be
more difficult to cope with due to strong variation in rejections and ultimately the
composition of product water. Every 1 °C increase in temperature brings about a 3-5%
increase in permeability of ions and water [238]. This can translate to 0.1 to 0.2 mS.cm-
1 in conductivity for a 5 °C change in inlet temperature where flux is maintained at
constant levels [236]. Alternatively, where it is not controlled flux can vary significantly.
Variations in water quality can place significant demands on the treatment process and
result in fluctuations in the product water quality. Water sourced from areas where fresh
and salt water mix can be significantly influenced by tidal variations. High tides will
result in higher salinity for the sources water while low tide will give the opposite. This
can interfere with the running of the plant.
3.7.3.2 Issues related to the treatment
Boron rejections in reverse osmosis are very low ranging from 30 to 90 % for a single
RO pass under a neutral pH [228]. This can result in a boron content of 1 to 2.5 mg.L-1
in product water from sea water [228]. This has raised concerns for irrigation and many
large scale desalination projects that provide water to irrigators as well as for drinking
uses multiple passes specifically to deal with this issue [228]. It is also possible to polish
RO treated seawater with ion exchange or adsorption based technologies.
Single pass RO treatment, while reducing salt content, can still leave a significant
quantity of salt in the permeate. Typical value quoted for total dissolved solids
concentrations after one RO pass range from 300 to 500 mg.L-1 [226, 228, 235, 238,
239]. Keeping in mind that calcium and magnesium are more easily rejected than
sodium [230] and the concentration of sodium is significantly higher than calcium and
magnesium in seawater (See Table 3.9), this could be detrimental to clay or loam based
98
soils. However, keeping in mind that sea water can only be sourced from coastal areas
and these soils are typically sandy, this may be less of an issue.
The age of the system will also impact on the quality of RO permeate. Degradation of
membranes over time leads to a loss in rejection. This has been quantified as being 10%
increase in permeability for each year of operation [238]. The use of RO systems for
desalination needs to keep this property in mind when aiming for a specific water
quality.
3.7.4 Inherent Advantages
Sea water desalination, if designed correctly, is the only water source that is truly
drought proof. The oceans represent a vast and constant supply of water that, with the
proper treatment, can be made suitable for irrigation.
While treatment processes are very energy intensive, they have been shown to integrate
well with renewable energy and research in this field is quite strong.
3.7.5 Disadvantages
Energy requirements for desalination can be high especially when compared to other
water treatment techniques. This impacts particularly on the ongoing costs of water
treatment. While there have been numerous successes in integrating renewable energy
this comes with increased capital costs.
The high energy requirement also leads to poor public perception when compared to
other water sources, although opinion is still generally favourable. Integration with
renewable energies should help with these issues.
Where the water is not properly treated boron and salinity may be an issue for irrigators.
Where this is the case coarse low clay soils should be used and clipping should always be
removed after mowing. Using these two management strategies should help to reduce
the impacts of poorer quality water.
The formation of a concentrated waste stream can complicate sea water treatment due
to disposal concerns. Discharge to sewers is not likely to be an option due to the high
salinity of the waste stream. Location near the sea or bay may help with disposal,
particular where low recovery systems are used as these wastewaters are only slightly
more concentrated than the seawater they were drawn from. Licensing would however
be required for the discharge.
3.7.6 Conclusions
In combination with renewable energy and careful waste management, desalination of
saline water would be considered one of the more sustainable water sources. It is the
only water supply considered here that is truly drought proof. While some treatment
techniques may produce water that is high in boron or salt content, this is generally
manageable.
99
Chapter 4 - Conclusions A range of sustainable options for sports fields have been presented. These range from
changes to turf types to changing the irrigation water.
A change from cool-season turfs to warm-season or artificial turfs will help to reduce
water demand. Concerns that typically arise about changes in gameplay, injury rates and
appearances are not necessarily too significant. Gameplay characteristics such as ball
bounce and ball roll will change with changes in turf surface. However turf surfaces seem
to generally remain within the requirements specified by the sport’s regulatory bodies.
Differences in gameplay will only come about through perceptions of surfaces, as has
been witnessed in soccer on artificial turfs. In this case however it was found the
sportsmen adapted to the changed conditions, limiting the impact. Injury rates between
the three turf types are generally similar, although there is an increase in the incidence
of minor injuries such as abrasions and turf burn on artificial turfs. The major
consideration with turf appearance is with winter dormancy of warm-season turfs. This
can lead to significant discoloration. There are solutions however with hybrid couch
grasses such as Wintergreen having been specifically bred to retain their colour of
winter. Overseeding with cool-season grasses during winter will reduce the water
requirements over summer months, while maintaining the more traditional cover over
winter.
Changes in irrigation delivery can be brought about by utilising subsurface techniques,
such as subsurface drip or subirrigation, instead of sprinkler or spray. Of these
subirrigation appears to be the least water intensive with 50-90% reductions in water
use compared to sprinklers. Subsurface drip irrigation is more complicated in that it does
not always bring a reduction in water usage, however the quality of the turf and
maintenance requirements were seen to reduce.
Six alternative water sources were considered:
• Rain water
• Storm water
• Grey water
• Black water
• Ground water
• Desalinated water
Of the six, desalinated water is the only true drought proof water source, while grey
water and black water recycling can be drought tolerant. The small volume generally
collected as rain water typically means it is useful as a supplement but not as a sole
source of water. Ground water recharge rates can also be slow making its use
unsustainable, aquifer recharge using another water source can help to alleviate storage
concerns while ensuring sustainable groundwater use.
Water qualities vary significantly, but the main concerns comes from salinity, metals and
boron concentrations in the wastewater streams. Salinity is a concern for recycled black
water, grey water, some ground water and desalinated sea water. It is of particular
concern to the stability of the soil, particularly clays. Where salinity is high calcium
addition is recommended and irrigation should be limited to sandy loam soils and
100
coarser. Continual monitoring of the soil would also be required to ensure its ongoing
structural stability.
Metals of concern in most alternative water sources revolve around copper and zinc.
These corrosion product are of particular concern in some rain water and storm water
sources as they are available at concentration that can be toxic to turf. Catchment
management to reduce the presence of copper and galvanised metal surfaces and pipes
should reduce the risk of contamination from these sources. Where this is not possible,
ongoing soil monitoring should be practices.
Boron toxicity is the final component of concern, and though it has been identified in the
past as a potential problem to recycled water cultural practices and product
reformulation have limited this. Boron is really only of concern in desalination from sea
water, due to the poor removal efficiency of boron in traditional technologies. Small scale
systems may not be able to effectively remove boron and leave the turf exposed to
toxicity issues. Removal of turf clipping after mowing should reduce this, but care should
be taken when using desalinated seawater as a source of irrigation water.
101
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